Audio network system and method of detecting topology in audio signal transmitting system

ABSTRACT

In an audio network system constructed from a main node and a plurality of satellite nodes each having a plurality of ports, the main node generates and transmits a main packet including audio signals of a plurality of channels. Each satellite node selects one of the plurality of ports in turn, and confirms whether the main packet arrives at the selected port every predetermined period or not. When the main packet arrives at the selected port every predetermined period, the main packet is received via the port by continuing selection of the port. In the case where reception of the main packet is lost, one is selected from the plurality of ports in turn, the operation to confirm arrival of the main packet is restarted, and another port at which the main packet arrives at the present stage is automatically found.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on, and claims priority to, JP PA 2008-294915filed on 18 Nov. 2008, JP PA 2008-308864 filed on 3 Dec. 2008, JP PA2008-308865 filed on 3 Dec. 2008 and JP PA 2008-308866 filed on 3 Dec.2008. The disclosure of the priority applications, in its entirety,including the drawings, claims, and the specification thereof, isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a network system constructed from aplurality of nodes, and particularly relates to an audio network systemfor transmitting audio signals. The present invention also relates to anaudio signal transmitting system that transmits an audio signal from atransmitting device to a receiving device in real time. The presentinvention also relates to a method of detecting topology (networkstructure) in an audio signal transmitting system that transmits anaudio signal from a transmitting device to a receiving device in realtime, and to an audio network system with a function to detect topology.

2. Description of the Related Art

Routing (route control) is a technique to find a route for transmittinga packet of information between nodes on a computer network systemconstructed from a plurality of nodes. When a route is turned out, it ispossible to transmit information by repeating transfer between nodes,that is, from an originating node to a node of a final destination alongthe route. In a conventional computer network system, each node holds arouting table for determining a route in accordance with an address ofthe destination, determines a route depending on an address added to apacket in accordance with this routing table, and transfers the packetalong the determined route.

For example, in the general-purpose network system such as the Internet,in the case where a failure occurs on a route to transfer information(packet), it is possible to avoid the failure by dynamically controllingroute information. Controlling route information dynamically is referredto as “dynamic routing”. The dynamic routing is a technique toautomatically generate and update a routing table in each node, and toautonomously determine another route using existing nodes by each node.The dynamic routing is normally carried out by means of a routingprotocol and path determination algorithm. The routing protocol is aprotocol for exchanging routing tables between nodes each other. Thepath determination algorithm is algorithm for generating a routing tablein each node. As the path determination algorithm, distance vectoralgorithm (hereinafter, referred to as “DVA”) and link state algorithm(hereinafter, referred to as “LSA”) are known.

The DVA is a method of determining an optimum route on the basis of“cost” recorded in a routing table that each node holds. The “cost” is anumerical value assigned to each node, and cost of a route connectedbetween two nodes is expressed by the sum total of costs between nodesthrough the route. A list of destination nodes (destinations of apacket), cost of a route for each destination, and the most recent node(“next partner (next hop)”) with which the node is to interact for eachdestination are recorded in the routing table.

At a first stage for determining an optimum route in a network, eachnode holds only information on “which is its neighboring node” and“cost” therebetween as a routing table. Then, data on the routing tablesare periodically exchanged between the nodes each other, and the routingtable of each of the nodes is updated using the exchanged data. Throughthis operation, each node records the best “next partner” and the best“cost” for oneself with respect to any destination node in the routingtable held by the node, and it is possible to determine the optimumroute on the basis of the table.

In the case where a node in the network is left out, in all nodes ineach of which the node is set to the “next partner”, destruction andreconstruction of the routing table is carried out. Information on thereconstructed routing table is transmitted to the neighboring nodes ofthe node in turn, and each node that receives the data updates therouting table of the node using the data. As a result, each existingnode can find the best route for all of reachable destination nodesexcept for the left-out node.

In the LSA, each node broadcasts data on “which are neighboring nodes ofthe node” to the whole network, generates a network map by itself on thebasis of data broadcasted from all other nodes, and determines theshortest route to other nodes using the generated network map by itself.Each node then generates a routing table using information on thedetermined shortest route with respect to all destination nodes. Eachnode can find the best “next partner” for the node to any destinationnode on the basis of the generated routing table.

Further, heretofore, there has been an audio network system in whichelectronic music instrument, a professional audio apparatus, a personalcomputer and the like are connected to a network, and audio signals formultiple channels are transferred between nodes thereof. As techniquesto carry out packet communication of audio signals and the like in theaudio network system, there have been known “mLAN” (for example, see thefollowing Patent Document 1 and the like) proposed by the applicant ofthis application, “EtherSound” (registered trademark) disclosed in thefollowing Patent Document 2, an asymmetric transmission network systemdisclosed in the following Patent Document 3, and “Cobranet” (RegisteredTrademark) disclosed in the following Non-Patent Document 1.

[Patent Document 1] Japanese Patent Application Laid-open PublicationNo. 2000-278354

[Patent Document 2] U.S. Pat. No. 7,089,333

[Patent Document 3] U.S. Pat. No. 5,764,917

BIAMP Systems/Audia Digital Audio Platform document entitled “What isCobraNet”

In a technique of a conventional dynamic routing, as described above, arouting table for determining a route in accordance with an address of adestination is required to be generated and updated in each node. Thus,a very complex process is necessary in each node, whereby it causescomplexity of route control in each node. Therefore, in the conventionalaudio network system, dynamic routing could not have been carried outwith simple control. In particular, in the audio network system, sinceeach node is a musical apparatus such as electronic music instrument, anaudio amplifier and a speaker, it is desired to carry out the dynamicrouting with a simple technique without complex control.

Further, in the audio network system as described above, it is known touse a reference signal called a word clock in order to synchronize withprocessing timing of an audio signal (sampling clock) among a pluralityof nodes. As one example, it is thought that a node (at a receivingdevice side) that receives a packet for transmitting an audio signalgenerates a word clock on the basis of timing when the packet reaches,and processes the audio signal of the received packet on the basis ofthe generated word clock.

Now, the larger a size of a packet for transmitting an audio signalamong respective nodes is, the better transfer efficiency of the audiosignal becomes. However, in the case where a word clock is generated ina node that receives the packet (at the receiving device side) on thebasis of timing when the packet reaches when the packet size is set soas to be larger, there has been a defect that stability of the wordclock becomes lower, and lag time between the word clock of a node thattransmits the packet (at a transmitting device side) and the word clockof the receiving device side becomes larger.

Further, in the audio network system as described above, one packetincluding sample data containing a plurality of samples about audiosignals for a plurality of channels was generated in the node thattransmits the audio signal (transmitting device) every predeterminedperiod of time, and the generated packet was transmitted to the nodethat receives the audio signals (receiving device). Note that atransmitting cycle of the packet in the audio network system becomeslonger than a sampling period of the audio signal (i.e., a period of thetransmitting cycle is longer than the sampling period). Therefore, asample of a plurality of audio signals can be contained in a singlepacket.

For this reason, the larger a size of a packet for transmitting audiosignals among respective nodes is, the more samples can be included inthe packet every transmitting cycle of the packet. Thus, transferefficiency of audio signals becomes good. However, there has been aproblem that, in the case where a transmission error of a packet occurs,the audio signal for one packet in which the transmission error occurredis lacking, and a period to output “silent” at the receiving device sideis to be generated. The larger the packet is (that is, as it is laid outwith the emphasis on transfer efficiency), a silent period at atransmission error becomes longer.

Further, in the conventional audio network system, any node in thenetwork system became a management node for managing topology (networkstructure) of the network system. In one example of the conventionalmethod of detecting topology, the method includes: detecting a nodeconnected to each port of each node in the network system; informing themanagement node of its detection result; making up reports (detectionresults) received from the respective nodes in the network system bymeans of the management node; and detecting topology (network structure)of the network system on the basis of the result thus made up. Namely,in the conventional method of detecting topology, there has beendisadvantage that complicated processes must be carried out in whicheach node detects other nodes connected to ports thereof and themanagement node is informed of its detection result. In particular,since each node in the audio network system is musical instrument suchas electronic instrument, an audio amplifier and a speaker, it ispreferable that detection of topology can be carried out with a simpletechnique without requiring complicated control.

SUMMARY OF THE INVENTION

The present invention is made in consideration of the circumstancesdescribed above, and it is an object of the present invention to providean audio network system capable of automatically changing routes toavoid a failure (dynamic routing) with relatively simple control evenwhen the failure occurs in the audio network system.

Further, it is another object of the present invention to provide anaudio signal transmitting system in which a receiving device of packetscan generate a clock signal (second clock) having little lag timebetween a clock (second clock) and a clock (first clock) at atransmitting device side with high stability as the clock (second clock)for synchronizing with the sampling clock among a plurality of nodeseven though a size of a packet for transmitting an audio signal becomeslarge.

Moreover, it is still another object of the present invention to providean audio signal transmitting system capable of avoiding occurrence of aperiod for outputting “silent” at a receiving device side even in thecase where a transmission error of a packet occurs.

Further, it is still another object of the present invention to providea method of detecting topology in an audio network system capable ofdetecting topology (network structure) of the network system with asimple technique without requiring a complicated process at each node,or an audio network system having a function to detect topology.

In order to achieve the above-mentioned objects, there is provided anaudio network system including a main node having at least one port, aplurality of satellite nodes each having a plurality of ports, and aplurality of cables that connects one port of one node of the main nodeand the plurality of satellite nodes to one port of another node of themain node and the plurality of satellite nodes, wherein the main nodeincludes: an input section that inputs audio signals of a plurality ofchannels to the main node; and a transmitting section that generates amain packet including the audio signals of the plurality of channelsinputted by the input section for every predetermined period in place ofthe main node, and transmits the main packet via the port of the mainnode, and wherein each of the plurality of satellite nodes includes: areceiving section that selects one of the plurality of ports of thesatellite node in turn, confirms whether the main packet arrives at theselected port every predetermined period, and, when the main packetarrives at the selected port every predetermined period, receives themain packet via the port by continuing the selection of the port; atransmitting section that transfers the main packet received by thereceiving section via another port other than the selected port of thesatellite node; and an output section that extracts an audio signal of adesired channel from the main packet received by the receiving sectionto output the extracted audio signal.

Each satellite node selects one of the plurality of ports by means ofthe receiving section in turn, and confirms whether or not the mainpacket arrives at the selected port every predetermined period. When themain packet arrives at the selected port every predetermined period, thesatellite node receives the main packet via the port by continuingselection of the port. Therefore, in the case where reception of themain packet is lost at the selected port, the satellite node restartsthe operation to select one of the plurality of ports in turn and toconfirm whether or not the main packet arrives at the selected portevery predetermined period, whereby the satellite node can automaticallyfind another port at which the main packet arrives every predeterminedperiod at the present stage.

Further, the present invention is an audio network system furtherincluding: another main node having one port connected to one port ofone node of the plurality of satellite nodes by means of the cable,wherein the another main node includes: an input section that inputsaudio signals of a plurality of channels to the another main node; areceiving section that confirms whether or not a main packet arrives atthe port of the another main node every predetermined period, and, whenthe main packet arrives at the port, receives the main packet via theport; and a transmitting section that, when the main packet does notarrive, generates a main packet including the audio signals of theplurality of channels inputted from the input section everypredetermined period in place of the main node, and transmits the mainpacket via the port of the another main node.

Further, the present invention is an audio network system furtherincluding: another main node having a plurality of ports, each of theplurality of ports being connected to one port of each of the pluralityof satellite nodes by means of the cable, wherein the another main nodeincludes: an input section that inputs audio signals of a plurality ofchannels to the another main node; a receiving section that confirmswhether or not a main packet arrives at any one port of the plurality ofports of the another main node every predetermined period, and, when themain packet arrives at any one port, receives the main packet via thecorresponding one port; a first transmitting section that, when the mainpacket arrives at the corresponding one port, transfers the main packetreceived by the receiving section via a port other than thecorresponding one port of the another main node; and a secondtransmitting section that, when the main packet does not arrive at thecorresponding one port, generates a main packet including the audiosignals of the plurality of channels inputted from the input sectionevery predetermined period in place of the main node, and transmits themain packet via the plurality of ports of the another main node.

The another main node confirms whether or not a main packet arrives at aport every predetermined period by means of the receiving section. Whenthe main packet arrives at the port, the another main node receives themain packet via the port. When the main packet does not arrive, theanother main node generates a main packet including audio signals of aplurality of channels inputted from the input section everypredetermined period in place of the main node, and transmits thegenerated main packet via the port of the main node by the transmittingsection. Therefore, when transfer of the main packet is lost on theaudio network system, the another main node can be automaticallypromoted to the main node to carry out transmission of a main packet.

According to the present invention, the satellite node can automaticallyfind another port at which the main packet arrives every predeterminedperiod at the present stage with simple control to select one of theplurality of ports in turn and to confirm whether the main packetarrives at the selected port every predetermined period or not.Therefore, the present invention achieves a beneficial effect that, eventhough a failure occurs in connection between nodes in the audio networksystem, reception of the main packet and output of the audio signals canbe continued without using a routing table.

Further, according to the present invention, when transfer of a mainpacket is lost on the audio network system, another main node isautomatically promoted to a main node, and carries out transmission of amain packet. Therefore, the present invention achieves a beneficialeffect that it is possible to continue the operation of the audionetwork system.

Therefore, according to the present invention, it is achieved abeneficial effect that, even though a failure occurs in the audionetwork system, it is possible to avoid the failure with relativelysimple control by automatically changing routes (dynamic routing).

According to another aspect of the present invention, there is providedan audio signal transmitting system, including: a transmitting device;and at least one receiving device connected to the transmitting deviceusing a cable, wherein the transmitting device includes: a clockgenerator that generates a first clock; a first period generator thatrepeatedly generates a first period on the basis of the first clockgenerated by the clock generator; an input section that inputs audiosignals of a plurality of channels, the audio signals being synchronizedwith the first clock; and a transmitting section that generates a packetevery first period generated by the first period generator and transmitsthe packet, the packet including a plurality of clock signals embeddedat constant intervals each corresponding to a divisor of the firstperiod and the audio signals of the plurality of channels inputted bythe input section, and wherein the receiving device includes: areceiving section that receives the packet transmitted by thetransmitting device; a clock generator that generates a second clock onthe basis of timing when the receiving section receives the plurality ofclock signals embedded in the packet; and an output section thatextracts an audio signal of one channel from the packet received by thereceiving section, and outputs the extracted audio signal insynchronization with the second clock generated by the clock generator.

The transmitting section of the transmitting device generates a packetincluding a plurality of clock signals embedded at every constant timeinterval corresponding to a divisor of the first period and an audiosignal of a plurality of channels inputted by the input section everyfirst period, and transmits it. Therefore, the receiving device cangenerate a second clock on the basis of reception timing (a period ofevery constant time interval) of each clock signal embedded everyconstant interval in the packet received from the transmitting device;synchronize with the generated second clock; and output the audio signalextracted from the received packet.

Further, as one preferred embodiment of the present invention, in theaudio signal transmitting system, there is an empty period in which anaudio signal is not contained between a packet and a subsequent packetof the packet transmitted by the transmitting device in every firstperiod, and the receiving device can transmit data to the transmittingdevice during the empty period.

The receiving device can take data corresponding to the transmittingdevice during an empty period between a packet and a subsequent packetto transmit the data to the transmitting device.

According to the present invention, the receiving device can generatethe second clock on the basis of the reception timing of the clocksignal having a period (i.e., the constant time interval) shorter thanthe first period for transmitting the packet. Therefore, a beneficialeffect that even in the case where a size of a packet for transmittingan audio signal becomes larger, the second clock having small lag timewith the first clock of the transmitting device side can be generatedwith high stability compared with a conventional technique to generate aword clock in synchronization with timing when the packet reaches thereceiving device, is achieved.

According to still another aspect of the present invention, there isprovided an audio signal transmitting system, including: a transmittingdevice; and at least one receiving device connected to the transmittingdevice using a cable, wherein the transmitting device includes: an inputsection that inputs a sample of an audio signal every sampling period; agrouping section that groups, every predetermined period longer than thesampling period, a plurality of samples of audio signals inputted in thepredetermined period by the input section into a first group of oddnumber samples and a second group of even number samples; a codegenerator that generates a first error check code based on the firstgroup of the odd number samples and a second error check code based onthe second group of the even number samples; and a transmitting sectionthat generates and transmits a packet including the first group of theodd number samples, the first error check code, the second group of theeven number samples and the second error check code every predeterminedperiod, and wherein the receiving device includes: a receiving sectionthat receives the packet transmitted by the transmitting device; anextracting section that extracts the first group of the odd numbersamples, the first error check code, the second group of the even numbersamples and the second error check code from the received packet; anerror check section that checks, using the extracted first error checkcode, whether a first error occurs in the extracted first group of theodd number samples or not, and checks, using the extracted second errorcheck code, whether a second error occurs in the extracted second groupof the even number samples or not; and an output section that generatesand outputs a silent audio signal in the case where a check result ofthe error check section is each of the first and second errors, theoutput section generating and outputting an audio signal on the basis ofthe second group of the even number samples in the case of the firsterror, the output section generating and outputting an audio signal onthe basis of the first group of the odd number samples in the case ofthe second error, the output section generating and outputting an audiosignal on the basis of the first group of the odd number samples and thesecond group of the even number samples in the case where there is noerror.

The transmitting device groups, every predetermined period, theplurality of samples of audio signals inputted in the predeterminedperiod by the input section into the first group of odd number samplesand the second group of even number samples; generates the first errorcheck code based on the first group of the odd number samples and thesecond error check code based on the second group of the even numbersamples; and generates and transmits the packet including the firstgroup of the odd number samples, the first error check code, the secondgroup of the even number samples and the second error check code. Thereceiving device extracts the first group of the odd number samples, thefirst error check code, the second group of the even number samples andthe second error check code from the packet received from thetransmitting device; and checks, using the first error check code,whether a first error occurs in the first group of the odd numbersamples or not, and checks, using the second error check code, whether asecond error occurs in the second group of the even number samples ornot. The output section of the receiving device generates and outputsthe silent audio signal in the case where the check result of the errorcheck section is each of the first and second errors, the output sectiongenerating and outputting an audio signal on the basis of the secondgroup of the even number samples in the case of the first error, theoutput section generating and outputting an audio signal on the basis ofthe first group of the odd number samples in the case of the seconderror, the output section generating and outputting an audio signal onthe basis of the first group of the odd number samples and the secondgroup of the even number samples in the case where there is no error.

Further, as one preferred embodiment of the present invention, theoutput section of the receiving device can be constructed so as togenerate the audio signal by alternately arranging the first group ofthe odd number samples and the second group of the even number samplesone sample by one sample in the case where there is no error.

Further, as one preferred embodiment of the present invention, theoutput section of the receiving device can be constructed so as togenerate the audio signal by generating a sample group of odd numbers onthe basis of the second group of the even number samples and alternatelyarranging the generated sample group of the odd numbers and the secondgroup of the even number samples one sample by one sample in the case ofthe first error.

Further, as one preferred embodiment of the present invention, theoutput section of the receiving device can be constructed so as togenerate the audio signal by generating a sample group of even numberson the basis of the first group of the odd number samples andalternately arranging the first group of the odd number samples and thegenerated sample group of the even numbers one sample by one sample inthe case of the second error.

The output section of the receiving device generates the audio signal byalternately arranging the first group of the odd number samples and thesecond group of the even number samples one sample by one sample in thecase where there is no error; or generates the audio signal bygenerating one sample group (i.e., first or second group) on the basisof the other sample group (i.e., second or first group) in which anerror does not occur and alternately arranging the sample group in whichan error does not occur and the generated sample group one sample by onesample in the case of the first or second error.

According to the present invention, in the case where a range of anaudio signal lost by an transmission error is within any one range ofthe first group of the odd number samples and the second group of theeven number samples even though the transmission error occurs when apacket is transmitted from the transmitting device to the receivingdevice, the audio signal can be generated on the basis of the group inwhich the error does not occur to be outputted. In such a case, asampling frequency of the audio signal is lowered and quality thereof isdegraded. However, it is much better than a situation that a period ofthe transmission error is to become “silent”. Namely, according to thepresent invention, a beneficial effect that even in the case where atransmission error of a packet occurs, it is possible to avoidoccurrence of a period for outputting “silent” at a receiving device.

According to still another aspect of the present invention, there isprovided a method of detecting topology in an audio network system, theaudio network system including: a main node having at least one port; aplurality of satellite nodes each having one M port and a plurality of Sports; and a plurality of cables, the plurality of cables including acable to connect one port of the main node to an M port of one satellitenode of the plurality of satellite nodes and a cable to connect an Mport of one satellite node of the plurality of satellite nodes to an Sport of another satellite node of the plurality of satellite nodes,wherein in the system, when one of the plurality of satellite nodesreceives any command transmitted from the main node via the M port ofthe satellite node, the satellite node transfers the received commandvia an S port of the satellite node, and the satellite node carries outa process based on the command and transmits a response to the commandvia the M port of the satellite node in the case where a destination ofthe received command is the satellite node, wherein, when any satellitenode other than the satellite node that has transmitted the responsereceives the response via an S port of the satellite node, the satellitenode that received the response transfers the received response via theM port of the satellite node, wherein in the system, when one of theplurality of satellite nodes receives an existence confirming commandfor all of the satellite nodes via the M port of the satellite node, thesatellite node transfers the received existence confirming command viaan S port of the satellite node, and the satellite node transmits anexistence confirming response to the received existence confirmingcommand via the M port of the satellite node in the case where thesatellite node is not prohibited from responding to the existenceconfirming command, wherein, in the case where the satellite node thathas received the existence confirming response is not prohibited fromtransferring the existence confirming response via the S port when anysatellite node other than the satellite node that has transmitted theexistence confirming response receives the existence confirming responsevia an S port of the satellite node, the satellite node transfers thereceived existence confirming response via the M port of the satellitenode, and wherein the method of detecting topology includes: a firststep of prohibiting all S ports of all of the satellite nodes fromtransferring an existence confirming response; a second step ofcontrolling the main node so as to transmit an existence confirmingcommand via a port of the main node, and of confirming a satellite nodeconnected to the port on the basis of an existence confirming responseto the transmitted existence confirming command, the existenceconfirming response being returned to the main node; a third step ofspecifying one of the plurality of S ports of the confirmed satellitenode; a fourth step of prohibiting the satellite node from transferringthe existence confirming response to S ports other than the S ports on aroute from the specified S port to the port of the main node, and ofprohibiting the satellite nodes on the route from the specified S portto the port of the main node from responding to the existence confirmingcommand; a fifth step of controlling the main node so as to transmit theexistence confirming command via the port of the main node, and ofconfirming the satellite node connected to the specified S port on thebasis of the existence confirming response to the transmitted existenceconfirming command, the existence confirming response being returned tothe main node; and a sixth step of specifying, in the case where thereremain S ports that have not been specified yet of the plurality of Sports of the satellite nodes that has been confirmed at the second andfifth steps, the remaining S ports one by one until all of the S portsof all of the confirmed satellite nodes are specified to repeat thefourth and fifth steps.

According to this method of detecting topology, the main node (1)prohibits all S ports of all of the satellite nodes from transferringthe existence confirming response by the first step; and (2) transmitsthe existence confirming command via the port of the main node toconfirm existence of the satellite node directly connected to the portof the main node on the basis of existence or absence of return of theexistence confirming response for the main node by the second step. Themain node (3) specifies one or one of the plurality of S ports of theconfirmed satellite node by the third step; (4) sets the S ports otherthan the S port on the route from the specified S port to the port ofthe main node to prohibition against transfer of the existenceconfirming response (that is, sets only the S ports on the route fromthe specified S port to the port of the main node to available fortransfer) and sets the satellite nodes on the route from the specified Sport to the port of the main node to prohibition against response by thefourth step; and (5) transmits the existence confirming command via theport of the main node, and confirms existence of the satellite nodeconnected to the specified S port on the basis of existence or absenceof return of the existence confirming response to the main node by thefifth step. The main node then (6) specifies all S ports of thesatellite node confirmed for the existence, and repeats the fourth andfifth steps until confirmation of existence of the satellite node to thedestination (access point) by the sixth step.

Further, the present invention according to still another aspect of,there is provided a method of detecting spare wire for connecting two Sports of two satellite nodes in the audio network system after executingthe method of detecting topology as described above, wherein in thesystem, when one of a plurality of satellite nodes receives a connectionconfirming command to the satellite node via the M port of the satellitenode, the satellite node transmits a search signal via an S portspecified by a port designator, the connection confirming commandincluding the port designator designating one S port of the satellitenode, wherein, when any satellite node other than the satellite nodethat has transmitted the search signal receives the search signal via anS port of the satellite node, the satellite node that received thesearch signal transmits a connection confirming response via the M portof the satellite node, the connection confirming response including anode ID of the satellite node and a port specifier indicating the S portvia which the satellite node has received the search signal, wherein,when any satellite node receives the connection confirming response viaan S port of the satellite node, the satellite node that has receivedthe connection confirming response transfers the received connectionconfirming response via the M port of the satellite node, and whereinthe method of detecting the spare wire includes: a seventh step ofspecifying one of particular S ports among a plurality of S ports of theconfirmed satellite node, each of said particular S ports being a portvia which said existence confirming response is not returned to the mainnode at the fifth step; an eighth step of controlling the main node soas to transmit the connection confirming command including the portdesignator designating the specified S port to the satellite node havingthe specified S port via a port of the main node, and of confirming thesatellite node connected to the specified S port on the basis of theconnection confirming response to the transmitted connection confirmingcommand, the connection confirming response being returned to the mainnode; and a ninth step of specifying remaining S ports one by one torepeat the eighth step in the case where there remain, in the specific Sports, the S ports via which the existence confirming response has notbeen returned to the main node at the fifth step or the S ports thathave not been specified yet of the S ports via which the search signalcorresponding to the connection confirming command transmitted at theeighth step has not been received.

According to this method of detecting spare wire, the main node (7)specifies the S port for which spare wire is confirmed by the seventhstep; and (8) transmits the connection confirming command to thesatellite node having the specified S port, and confirms existence ofthe satellite node connected to the specified S port by the spare wireon the basis of existence or absence of the connection confirmingresponse to the main node by the eighth step. The main node then (9)repeats the eighth step until all S port required for detection of thespare wire are checked by the ninth step.

Further, According to still another aspect of the present invention,there is provided an audio network system, including: a main node havingat least one port; a plurality of satellite nodes each having one M portand a plurality of S ports; and a plurality of cables, the plurality ofcables including a cable to connect one port of the main node to an Mport of one satellite node of the plurality of satellite nodes and acable to connect an M port of one satellite node of the plurality ofsatellite nodes to an S port of another satellite node of the pluralityof satellite nodes, wherein in the system, each of the plurality ofsatellite nodes includes: a command transferring and responsetransmitting section that transfers, when to receive any commandtransmitted from the main node via the M port, the received command viaan S port of the satellite node, the command transferring and responsetransmitting section carrying out a process based on the command andtransmitting a response of the satellite node to the received commandvia the M port in the case where a destination of the received commandis the satellite node; a response transferring section that transfers,when to receive the response transmitted by a command transferring andresponse transmitting section of other satellite node via the S port,the received response made by the other satellite node via the M port ofthe satellite node; a transfer prohibiting section that prohibits, whento receive a transfer prohibiting command from the main node via the Mport, a transfer by the response transferring section of the responsemade by the other satellite node, the response being received via the Sport specified by the transfer prohibiting command, the transferprohibiting section permitting the transfer of only S ports other thanthe specified S port; and a response prohibiting section that prohibits,when to receive a response prohibiting command for prohibiting aresponse to an existence confirming command from the main node via the Mport, the command transferring and response transmitting section fromtransmitting an existence confirming response made against the existenceconfirming command by the satellite node, wherein for carrying outdetection of topology in the audio network system, the main nodeincludes: a first transmitting section that transmits the transferprohibiting command for prohibiting all of the satellite nodes fromtransferring the existence confirming response from all of S ports via aport of the main node to prohibit all of the satellite nodes fromtransferring the existence confirming response from all of the S ports;a first confirming section that transmits the existence confirmingcommand via the port of the main node after the transfer prohibitingcommand has been transmitted by the first transmitting section, andconfirms the satellite node connected to the port of the main node onthe basis of the existence confirming response to the transmittedexistence confirming command, the existence confirming response beingreturned to the main node; a first specifying section that specifies oneof the plurality of S ports that the confirmed satellite node has; asecond transmitting section that transmits, via the port, the transferprohibiting command for prohibiting S ports, other than the S ports on aroute from the S port specified by the first specifying section to theport of the main node, from transferring the existence confirmingresponse, and transmits, via the port, the response prohibiting commandfor prohibiting the satellite nodes on the route from the specified Sport to the port of the main node from carrying out the existenceconfirming response to the existence confirming command; a secondconfirming section that transmits the existence confirming command viathe port after the transfer prohibiting command and the responseprohibiting command have been transmitted by the second transmittingsection, and confirms the satellite node connected to the specified Sport on the basis of the existence confirming response to thetransmitted existence confirming command, the existence confirmingresponse being returned to the main node; and a determining section thatspecifies, in the case where there remain S ports that have not beenspecified yet of the plurality of S ports of the satellite nodesconfirmed by the first and second confirming sections, the remaining Sports one by one until all of the S ports of all of the confirmedsatellite nodes are specified to repeatedly confirm the satellite nodeconnected to the S port specified by the second transmitting section andthe second confirming section.

Further, According to still another aspect of the present invention,there is provided the audio network system described above wherein eachof the plurality of satellite nodes further includes: a search signaltransmitting section that transmits, when to receive a connectionconfirming command for the satellite node via the M port, a searchsignal via one S port designated by a port designator, the connectionconfirming command including the port designator designating the S portof the satellite node; a connection confirming response transmittingsection that transmits, via the M port, a connection confirming responseincluding a node ID of the satellite node and a port specifierspecifying the S port via which the satellite node receives the searchsignal when a search signal transmitted by a search signal transmittingsection of other satellite node is received via an S port; and aconnection confirming response transferring section that transfers thereceived connection confirming response via the M port when a connectionconfirming response transmitted by a connection confirming responsetransmitting section of other satellite node is received via an S port,and wherein for detecting spare wire to connect two S ports of twosatellite nodes in the audio network system after detecting thetopology, the main node further includes: a second specifying sectionthat specifies one of the specific S ports of the plurality of S portsof the confirmed satellite node, the existence confirming response beingnot returned from the specific S ports in the second confirming section;a third confirming section that transmits, via the port of the mainnode, the connection confirming command including the port designatordesignating the specified S port to the satellite node having the S portspecified by the second specifying section, and confirms the satellitenode connected to the specified S port on the basis of the connectionconfirming response to the transmitted connection confirming command,the connection confirming response being returned to the main node; anda second determining section that specifies remaining S ports one by oneto repeatedly confirm the satellite node connected to the S portspecified by the third confirming section in the case where thereremain, in the specific S ports, the S ports via which the existenceconfirming response has not been returned to the main node in the secondconfirming section or the S ports that have not been specified yet ofthe S ports via which the search signal corresponding to the connectionconfirming command transmitted in the third confirming section has notbeen received.

Namely, the present invention can construct and implement the audionetwork system having a function to detect topology, and further theaudio network system having a function to detect spare wire.

According to the present invention, using simple communicationprotocols, such as transmission of the “existence confirming command” bythe main node, return of the “existence confirming response” by thesatellite node that received the “existence confirming command”, remotecontrol to “prohibit transfer” for S ports of satellite nodes, andremote control to “prohibit response” for each of the satellite nodes,the main node can detect connection (topology) of all of the satellitenodes on the network. In this case, each of the satellite nodes ismerely required to carry out simple processes such as a response to the“existence confirming command” (existence confirming response) andreception of remote control to prohibit transfer for each of the Sports. Thus, it is no need for the satellite node to carry outcomplicated processes such as a process to detect a neighboring node byoneself. Therefore, a beneficial effect that topology (networkstructure) of the network system can be detected with a simple techniquewithout need to carry out a complicated process at each node isachieved. The method of detecting topology according to there isprovided not suitable for detection of topology that the system uses tocontrol the nodes, but for detection of topology that the systempresents its users (for example, topology presented by display on ascreen or the like).

Further, according to the present invention, by simple communicationprotocols including transmission of the “connection confirming command”by the main node, transmission of the “search signal” by the satellitenode that received the “connection confirming command”, and return ofthe “connection confirming response” by the satellite node that receivedthe search signal, the main node can detect spare wire of the satellitenodes. In this case, the satellite node is merely required to carry outsimple processes (transmission of the “search signal” according to the“connection confirming command”, and transmission of the “connectionconfirming response” according to the “search signal”), and is notrequired to carry out complicated processes such as detection of theneighboring nodes. Therefore, a beneficial effect that spare wire of thenetwork system can be detected with a simple technique without need tocarry out a complicated process at each node is achieved.

The foregoing and other objects, features and advantages of the presentinvention will become more readily apparent from the following detaileddescription of a preferred embodiment of the present invention thatproceeds with reference to the appending drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram for explaining a configuration example of anaudio network system according to the present invention.

FIG. 2 is a block diagram showing another configuration example of theaudio network system in FIG. 1.

FIG. 3 is a view for explaining a structure of a packet to betransmitted in the audio network system in FIG. 1.

FIGS. 4A-4D are views for explaining procedures to generate a mainpacket of FIG. 3.

FIG. 5A is a block diagram showing an example of a hardwareconfiguration of a satellite node, and FIG. 5B is a block diagramshowing an example of a hardware configuration of a main node.

FIG. 6 is a block diagram showing a detailed configuration of anoscillator in the satellite node of FIG. 5.

FIGS. 7A-7D are views for explaining a detecting process of routecontrol and topology, and a view showing an example of a configuration(connection status between nodes) of the audio network system.

FIG. 8 is a flowchart showing an example of a base process.

FIG. 9 is a flowchart showing an example of a main packet transmittingprocess.

FIG. 10 is a timing chart of a main packet generating and transmittingoperation.

FIG. 11 is a flowchart showing an example of an M port setting processin the satellite node.

FIG. 12 is a flowchart showing an example of an M port setting processin the main node.

FIG. 13 is a flowchart showing an example of a packet transferringprocess in the satellite node.

FIG. 14 is a flowchart showing an example of a main packet receivingprocess in the satellite node.

FIG. 15 is a timing chart of a reception operation of a main packet anda reproduction operation of an audio signal.

FIGS. 16A-16H are views for explaining network structure data.

FIG. 17 is a flowchart showing an example of a topology detectingprocess in the main node.

FIG. 18 is a flowchart for explaining an operation in response to atransfer prohibiting command in the satellite node.

FIG. 19 is a flowchart for explaining an operation in response to anexistence confirming command in the satellite node.

FIG. 20 is a flowchart for explaining an operation when transmission ofa satellite packet is set in the satellite node.

FIG. 21 is a flowchart for explaining an operation in response to aresponse prohibiting (or permitting) command in the satellite node.

FIG. 22 is a flowchart showing an example of a connection (spare wire)detecting process in the main node.

FIG. 23 is a flowchart for explaining an operation in response to aconnection confirming command in the satellite node.

FIG. 24 is a flowchart for explaining an operation when reception of asearch signal is detected in the satellite node.

FIG. 25 is a flowchart for explaining an operation in response to thesearch signal in the satellite node.

FIG. 26 is a flowchart for explaining an operation when a screenselecting (screen switching) operator is operated in the main node.

FIG. 27 is a flowchart for explaining an operation when a value changingoperator is operated in the main node.

FIG. 28 is a flowchart for explaining an operation in response to avalue changing command for parameters in the satellite node.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will now be described in detailwith reference to the accompanying drawings.

<Configuration of Audio Network System>

FIG. 1 is a schematic block diagram showing an example of a wholeconfiguration of an audio network system according to the presentinvention. An audio network system is constructed from: one main node (Mnode) 1 having at least one port; a plurality (eight in FIG. 1) ofsatellite nodes (S nodes) 2 a to 2 h each having a plurality of ports;and a plurality of cables (connecting wire) each of which connects oneport of an arbitrary node of the main node 1 and the plurality ofsatellite nodes 2 a to 2 h to one port of another arbitrary node of themain node 1 and the plurality of satellite nodes 2 a to 2 h. In theconfiguration example of the audio network system in FIG. 1, each of thesatellite nodes 2 a to 2 h is connected to other node or nodes throughone or more port thereof. Therefore, there is one or more route from themain node 1 to each of the satellite nodes 2 a to 2 h for everysatellite node 2 a to 2 h.

An audio source (AS) 3 that supplies audio signals of a plurality ofchannels (for example, eight channels) to the main node 1 is connectedto the main node 1. The main node 1 is a node that transmits a mainpacket including the supplied audio signals. It is assumed that the mainnode 1 is a musical apparatus having a network function, such as anamplifier and an audio mixer, or a general-purpose computer, forexample.

Further, a sound system (SS) 4 for reproducing sounds in accordance withan audio signal is connected to each of the satellite nodes 2 a to 2 h.The sound system (SS) 4 reproduces sounds in accordance with an audiosignal included (or contained) in the main packet that is received fromthe main node 1. In this embodiment, it is assumed that each of thesatellite nodes 2 a to 2 h (including sound system (SS) 4) is a speakerapparatus in which an amplifier is provided.

The main node 1 generates packet data including the audio signals of theplurality of channels supplied from the audio source 3 everypredetermined period, and transmits the generated packet data from aport with which the main node 1 is provided. The main packet transmittedfrom the main node 1 every predetermined period is transferred betweennodes connected to each other on the audio network system. Each of thesatellite nodes 2 a to 2 h receives the main packet via any one of theplurality of ports thereof, and extracts an audio signal of a channelnecessary for itself from the received main packet. Each of thesatellite nodes 2 a to 2 h then outputs the extracted audio signal tothe corresponding sound system 4, and transfers the received main packetto other satellite nodes via other ports than the port from which themain packet is received. Therefore, so long as any one route for each ofthe satellite nodes 2 a to 2 h is connected to the main node 1, thesatellite nodes 2 a to 2 h can receive the audio signals transmittedfrom the main node 1.

A route to transmit packet data from the main node 1 to each of thesatellite nodes 2 a to 2 h is selected by route control (routing), whichwill be described later in detail. The audio network system shown inthis embodiment has a feature in the route control. To make a furtherreference, the feature is that, in the case where a failure occurs inthe route for transmitting the packet data (for example, in the casewhere any node falls out, or the like), by searching a new route inroutes in which cables are arbitrarily connected (searching anotherroute) to automatically change routes, it is possible to avoid thefailure (that is, to carry out dynamic routing) with relatively simplecontrol.

FIG. 2 is a modified example of the configuration of the audio networksystem shown in FIG. 1. FIG. 2 shows a configuration example in whichone main node 5 is further added to the audio network system in FIG. 1,that is, a configuration example in which main nodes are duplexed(doubled). In FIG. 2, two main nodes 1 and 5 are respectively connectedto the audio network system, and an audio source 3 is connected to boththe main node 1 and the main node 5.

As shown in FIG. 2, in the configuration having a plurality (two ormore) of main nodes (the configuration in which main nodes aremultipexed), one of a plurality (two or more) of main nodes (forexample, main node 1) operates as a main node, and the other main nodes(for example, main node 5) operate as a satellite node. Namely, the mainnode 5 that operates as a satellite node receives a main packet via anyport, and transfers the received main packet to other satellite nodesvia other ports. Then, in the case where the main node 5 that operatesas a satellite node does not receive a main packet via any port (in thecase where the main node 1 disappears from the audio network system),the main node 5 is automatically promoted to a main node, and startsoperations as a main node. In this regard, illustration of a soundsystem connected to each of the satellite nodes is omitted in FIG. 2.

<Structure of Packet>

FIG. 3 is a view for explaining a structure of packet data flowing onthe audio network system. In FIG. 3, a horizontal axis indicates time,and one frame 6 on the time axis indicates a period (namely, a cycle) ofone milliseconds (one msec.), which is a unit of packet transfer, i.e.,a packet transmitting cycle. A main packet 7 and a satellite packet 8are transferred for every packet transmitting cycle (one msec.). Atransfer rate of data in this network system is 24.576 Mbit/sec., forexample. The main packet 7 has a header in the lead, a plurality ofclock signals and plural kinds of data after the header. The pluralityof clock signals and the plural kinds of data are reciprocally providedtherein. The main node 1 generates one main packet 7 every packettransmitting cycle, and transmits the main packet 7 from all ports ofthe main node 1 toward the satellite nodes. The satellite packet 8 is apacket to be generated and transmitted by the satellite nodes ifnecessary. The satellite packet 8 does not always come in every packettransmitting cycle.

The plurality of clock signals are included (or contained) in onepacket. The clock signal is a clock signal for synchronizing a samplingclock of the satellite nodes 2 a to 2 h side with a sampling clock ofthe main node 1 side.

In this embodiment, the clock signals are included (or contained) every83.3 μsec. in which the packet transmitting cycle (one msec.) is equallydivided into twelve. Namely, twelve clock signals are embedded in onepacket at even intervals. Data of 2048 bits (256 bites) including theclock signal are transferred every period of 83.3 μsec. Eleven pieces ofdata (Data 1 to Data 11) constituting the main packet 7 are included (orcontained) in the lead to eleventh periods of the periods of 83.3 μsec.in which the packet transmitting cycle (one msec.) is equally dividedinto twelve, and the satellite packet 8 is included in the last twelfthperiod. In this specification, a period (from the lead to the eleventhperiod of one packet) for transferring the main packet 7 is referred toas a “main packet period”, while the last twelfth period is referred toas a “satellite packet period”.

In this regard, in FIG. 3, the satellite packet 8 in the “satellitepacket period” is delayed with respect to the clock signal indicatingtiming to start the satellite packet period (the packet is drawn so asto be spaced against the clock signal). The satellite node thatgenerates the satellite packet 8 outputs the satellite packet 8 at thetiming of the clock signal in the satellite packet period. However, arelation between transfer delay at each connecting wire on the route tothe main node and time taken for transfer of the satellite packet ateach node causes the satellite packet 8 to delay with respect to theclock signal more toward an upstream side. In FIG. 3, such delay isexpressed.

Further, a header of a next main packet 7 is provided at the end of thesatellite packet period (that is, the end of the packet transmittingcycle). Namely, a header of a main packet 7 is provided in the end ofthe last packet transmitting cycle. In this regard, a header portion 9is a bit pattern indicating the lead of a packet.

FIG. 4 is a view for explaining an overview of procedures to generateone main packet 7. In this embodiment, a bit width of an audio signal isset to 24 bits, and a sampling rate thereof is set to 96 kHz. The packettransmitting cycle of one msec. described above corresponds to timeobtained by dividing the sampling clock into 96 pieces. Therefore, 96pieces of sample data (“S0” to “S95”) of 96 sampling periods areincluded (or contained) in the main packet 7 generated every packettransmitting cycle. Each piece of the sample data (“S0” to “S95”) is asample of audio signals of eight channels.

In FIG. 4A, the 96 pieces of sample data (“S0” to “S95”) are groupedinto a group of even samples (“S0”, “S2” . . . “S94”) and a group of oddsamples (“S1”, “S3”, . . . “S95”). In FIG. 4B, a set of the group ofeven samples (“S0”, “S2”, . . . “S94”) and a control signal (CTR) and aset of the group of odd samples (“S1”, “S3”, . . . “S95”) and a controlsignal (CTR) are generated, and error check information (EC) is added toeach set. The control signal (CTR) includes commands for the satellitenodes regarding route control and the like, and control data forremotely controlling signal processing of the respective satellite nodesfrom the main node 1. The error check information (EC) is informationfor checking an error in each of an even sample group (even numbersample group) and an odd sample group (odd number sample group) when theaudio signal of each channel is reproduced at each of the satellitenodes 2 a to 2 h that received the packet.

Thus, by dividing (grouping) the data constituting one main packet intotwo groups including the data in which the error check information isadded to the set of the even sample group and the control signal and thedata in which the error check information is added to the set of the oddsample group and the control signal, the audio signal can be reproducedusing the data of a group of the two groups, which is unaffected by atransmission error of a packet when the audio signal is reproduced atany satellite node even in the case where part of the data in the packethas been lost by means of the transmission error of the packet.

Twelve clock signals are embedded in one main packet, which areconstructed from the data in which the error check information is addedto the set of the even sample group and the control signal and the datain which the error check information is added to the set of the oddsample group and the control signal, at even intervals.

Namely, the data of one main packet (the data in which the error checkinformation is added to the set of the even sample group and the controlsignal and the data in which the error check information is added to theset of the odd sample group and the control signal) are equally dividedinto 11 pieces of data block “Data 1” to “Data 11” (FIG. 4C), each ofthe data blocks “Data 1” to “Data 11” is put between any two of the 12clock signals, and the header portion 9 is added to the load portion ofthe main packet (FIG. 4D). Thus, a main packet 7 in which 12 clocksignals are embedded in a period of a packet transmitting cycle (onemsec.) at even intervals is generated. In this case, a size of the mainpacket 7 is in the range of about 2,820 to 2,830 bytes.

As this embodiment, by separately embedding a plurality of clock signals(12 signals) in a main packet 7 to be transferred every predeterminedperiod (one msec.) at even intervals (83.3 μsec.), in each of thesatellite nodes, it is possible to generate a sampling clock used forreproduction of the audio signal in one packet transmitted every onemsec. on the basis of a plurality of clock signals every 83.3 μsec.Therefore, compared with the case where a sampling clock is generatedwith rough resolution synchronized with the transmitting cycle of a mainpacket 7, it is possible to generate a sampling clock (a sampling clockat the satellite node side) with high stability and with a small shiftagainst a sampling clock used at the main node that generates the mainpacket 7.

<Hardware Configuration>

FIG. 5 is a block diagram for schematically explaining a hardwareconfiguration of each of the satellite nodes 2 a to 2 h and the mainnode 1. FIG. 5A is a configuration example of the satellite node, whileFIG. 5B is a configuration example of the main node.

<Satellite Node>

In FIG. 5A, a satellite node includes four ports 10 a to 10 d. Numericalvalues increasing one by one from “0” are applied to the four ports 10 ato 10 d as port numbers (“port 0”, “port 1”, “port 2” and “port 3”). Anyone of the four ports 10 a to 10 d (“port 0” to “port 3”) becomes a mainport (M port) that receives a main packet transmitted from a main node1.

In a main packet period of a packet transmitting cycle (one msec.), afirst selector 11 selects the M port from the four ports 10 a to 10 d,and outputs the received main packet to a receiving and transferringsection 12 every packet transmitting cycle. In a satellite packetperiod, the first selector 11 selects one port, via which a satellitepacket is received, from the three ports (S ports) other than the Mport, and outputs the received satellite packet to the receiving andtransferring section 12. Further, a reception detecting signal conveyingthat packet data is started to receive at the port is outputted to thereceiving and transferring section 12 from each of the ports 10 a to 10d (indicated by a dotted line in FIG. 5A). The receiving andtransferring section 12 controls the first selector 11 so as to select aport via which the satellite packet is first received for each of thesatellite packet periods on the basis of the reception detecting signal(one that arrives first has a priority).

In this regard, the “M port” means a port that receives the main packetin the satellite node (that is, a port that faces the main node when thenetwork structure is hierarchically viewed along a packet transmissionroute). Further, the “S port” specifies ports of the four ports otherthan the M port.

The receiving and transferring section 12 carries out control to receivethe main packet and the satellite packet supplied from the firstselector 11 on the basis of control data stored in a control dataregister 18 (will be described later), control to extract various datafrom the received packet, and control to transfer the received packet toother node. Further, in the case where the satellite node generates andtransmits a satellite packet, the receiving and transferring section 12also carries out an operation to control transmission timing of thesatellite packet. The satellite node basically generates the satellitepacket including a response to the control signal and transmits thesatellite packet to the main node when the satellite node is adestination in a control signal (CTR) included in the received mainpacket. Details of each operation will be described later.

The main packet or the satellite packet to be transferred, which isoutputted from the receiving and transferring section 12, is inputted toa second selector 13 via one input, and the satellite packet outputtedfrom a satellite packet generating and transmitting section 20 isinputted via the other input. An output of the receiving andtransferring section 12 is basically selected to output. Whentransmission of the satellite packet is set by a control section 17,output of the satellite packet generating and transmitting section 20 isselected at the timing of a clock signal indicating the lead of asatellite packet period supplied from the receiving and transferringsection 12. In this regard, the present system is designed so that aplurality of satellite nodes do not generate and transmit satellitepackets at the same time, and therefore, no satellite packet to betransferred is sent from a downstream side of the route when a satellitepacket is transmitted from the satellite node. On the other hand, when asatellite packet to be transferred from the downstream side of the routeis transmitted, there is no need to transmit a satellite packet from thesatellite node.

A gate 14 is a gate for controlling opening and closing of each of thefour ports 10 a to 10 d (“port 0” to “port 3”). The gate 14 opens all ofthe ports other than the M port in the main packet period, and opensonly the specified M port in the satellite packet period. Therefore, themain packet is transferred to all of the satellite nodes that areconnected to the downstream side of the route of the satellite node, andthe satellite packet is transferred (transmitted) to only the specifiedM port.

An instruction register 15 is a register for writing various kinds ofinstruction data (control signal CTR) extracted from the received mainpacket by means of the receiving and transferring section 12 thereinto.A state information register 16 is a register for writing various kindsof state information such as confirmation of reception of the mainpacket thereinto.

Reception and transfer of the packet data (main packet and satellitepacket) via the ports 10 a to 10 d are controlled by the operations ofthe first selector 11, the receiving and transferring section 12, thesecond selector 13 and the gate 14 as described above.

The control section 17 is a microcomputer including a CPU and a memory.By executing various processes (will be described later in detail), thecontrol section 17 generates control data for controlling the receivingand transferring section 12, generates (or creates or reconstructs)response data to various commands written into the instruction register15, or generates values of various kinds of control parameters used forsignal processing of the signal processing section 21.

The control data register 18 is a register for holding the control datafor controlling the receiving and transferring section 12, which aregenerated by the control section 17. M port number data indicating the Mport of the satellite node, reception channel number data indicating achannel number necessary for the satellite node in the audio signals ofeight channels, and prohibited port data for instructing whethertransfer of the received satellite packet is permitted or prohibited foreach port of the four ports 10 a to 10 d (“port 0” to “port 3”) areincluded in the control data.

A response register 19 is a register for writing response data generatedby the control section 17 with respect to the command transmitted fromthe main node thereinto. Since the response data always address to themain node, data indicating a destination is not added to the writtenresponse data. When the response data are set to the response register19 by the control section 17, the satellite packet generating andtransmitting section (S packet generating and transmitting section) 20generates a satellite packet on the basis of the response data, andtransmits the generated satellite packet at the timing of a clock signalindicating the lead of the satellite packet period supplied from thereceiving and transferring section 12. An output of the satellite packetgenerating and transmitting section 20 becomes one input of the secondselector 13.

Further, the receiving and transferring section 12 buffers data of thereceived main packet (“Data 1” to “Data 11”) every packet transmittingcycle (every one msec.), extracts an audio signal of the channelnecessary for the satellite node from the buffered data on the basis ofthe reception channel number data stored in the control data register18, and carries out control to output the extracted audio signal to thesignal processing section 21 every sampling period (a process related toreproduction of an audio signal). At this time, the receiving andtransferring section 12 detects reception timing of a plurality of clocksignals embedded in the main packet at even intervals, and transmits itto the oscillator 22.

The oscillator (OSC) 22 synchronizes with the reception timing of theclock signal in the main packet, and generates a sampling clock (secondclock) that is a signal for defining a sampling period. FIG. 6 is a viewshowing a configuration example of the oscillator. The OSC 22 isconstructed from: a phase comparator 50 that compares a phase of afeedback signal with reception timing of the clock signal of the mainpacket; a frequency information generator 51 that generates frequencyinformation corrected in accordance with an output of the phasecomparator 50; an oscillator 52 whose oscillation frequency iscontrolled by an output signal of the frequency information generator51; and a divider 53 put between an output of the oscillator 52 and aninput of the phase comparator 50. Namely, an operation clock generatoris a frequency multiplier by means of a PLL (abbreviation for “PhaseLocked Loop”). The operation clock generator compares reception timingof the clock signal of the main packet with rising (or trailing) timingof the feedback signal, and adjusts frequency information so that aphase of a signal in which the clock signal from the receiving andtransferring section 12 and the output of the oscillator 52 are dividedinto eight in accordance with the comparison result keeps a givenrelation to output the frequency information to the oscillator 52. Theoscillator 52 generates a sampling clock (96 kHz) synchronized with theclock signal in accordance with the frequency information to output thesampling clock. The clock signal of the main packet is a clock of timingin which one transfer clock (one transmitting cycle=one msec.) isdivided into twelve, but corresponds to a signal in which the samplingclock (96 kHz) of the main node is divided into eight. By dividing thesampling clock of the satellite node into eight to synchronize it withthe phase of the clock signal of the main packet, as a result, thesampling clock generated in the satellite node is synchronized with thesampling clock of the main node.

The signal processing section 21 is constructed from a filter, acompressor, a delay (delay control), or an element such as a levelcontrol (damper). The signal processing section 21 carries out signalprocessing for a sample of the audio signal outputted from the receivingand transferring section 12 every sampling period indicated by thesampling clock outputted by the oscillator 22 to output the sample to adigital-to-analog converter (DAC) 23. A value of a parameter used forthe signal processing of the signal processing section 21 is suppliedfrom the control section 17. The DAC 23 converts the samples of theaudio signals for a plurality of channels, which are outputted from thesignal processing section 21, into analog signals every sampling periodindicated by the sampling clock outputted by the oscillator 22, andoutputs the analog signals to the sound system 4 (see FIG. 1).

<Main Node>

A configuration of the main node will be described with reference toFIG. 5B. The main node includes two ports (“port 0” 30 a and “port 1” 30b). Main operation of the main node is to generate a main packetincluding the audio signals supplied from the audio source (Referencenumeral 3 in FIG. 1) and to transmit it from the ports 30 a, 30 b.

An analog-to-digital converter (ADC) 31 converts analog audio signals ofeight channels inputted from an external audio source (Reference numeral3 in FIG. 1) into digital signals every sampling period indicated by thesampling clock (96 kHz) to output digital signals to a signal processingsection 32. The signal processing section 32 processes the audio signalsof the eight channels supplied from the ADC 31 on the basis of the valueof the parameter supplied from a control section 38 every samplingperiod (96 kHz) for each channel, and outputs the audio signals to amain packet generating and transmitting section 34. An oscillator (OSC)33 generates a sampling clock (first clock) of a predetermined samplingfrequency (for example, 96 kHz) on the basis of a system clock (notshown in the drawings), and supplies the sampling clock to the ADC 31and the signal processing section 32.

In this regard, although an example in which an input interface of theaudio signal is configured by the ADC 31 into which the analog signalsare inputted has been described in this embodiment, an input interfaceof a digital signal into which a digital audio signal is inputted may beutilized. In a configuration to input a digital signal, an externalsampling clock extracted from the digital signal or an external samplingclock separately supplied from a source of the digital signal may besupplied to the OSC 33, the OSC 33 may be caused to generate a samplingclock synchronized with the supplied external sampling clock.

The main packet generating and transmitting section 34 generates a mainpacket including the audio signals of the eight channels supplied fromthe signal processing section 32 and various kinds of instruction data(control signal CTR) supplied from an instruction register 35 at thetiming to transmit the main packet (packet transmitting cycle of everyone msec.), and outputs the generated main packet to a first selector36. Further, the main packet generating and transmitting section 34outputs the clock signal indicating the lead of the satellite packetperiod at the timing of the clock signal of the end of the main packetto a receiving and transferring section 42. Further, the main packetgenerating and transmitting section 34 generates clock signals forembedding into the main packet to be generated by the main packetgenerating and transmitting section 34 on the basis of the system clock(not showing in the drawings) every 83.3 s, and counts up the generatedclock signals to generate a pulse signal indicating a packettransmitting cycle whenever 12 pieces of the clock signals are countedup, thereby repeatedly generating the packet transmitting cycles everyone msec. Here, since both the main packet generating and transmittingsection 34 and the OSC 33 are synchronized with the same system clock(not shown in the drawings), the packet transmitting cycle generated bythe main packet generating and transmitting section 34 corresponds totime obtained by dividing the sampling clock generated by the OSC 33into 96 pieces. Namely, the main packet generating and transmittingsection 34 repeatedly generates the packet transmitting cycle (namely, afirst period) every time obtained by dividing the sampling clock(namely, the first clock) generated by the OSC 33 into 96 pieces.

An output of the main packet generating and transmitting section 34 andan output of the receiving and transferring section 42 are inputted tothe first selector 36. When the main node operates as a main node, thefirst selector 36 selects the output of the main packet generating andtransmitting section 34 to output it to a gate 37. When the main nodeoperates as a main node, the gate 37 opens the two ports 30 a, 30 b.Therefore, when the main packet generating and transmitting section 34generates and transmits the main packet at the timing to transmit themain packet, the main packet is transmitted from the two ports 30 a, 30b.

The control section 38 is a microcomputer including a CPU and a memory,and executes various processes (will be described in detail later). Morespecifically, the control section 38 generates values of various kindsof control parameters used for signal processing of the signalprocessing section 32 in accordance with an operation of an operator 43to supply the values to the signal processing section 32, generatesvarious instructions (including parameters for remote control) for thesatellite nodes to write them into the instruction register 35, orgenerates control data to control the receiving and transferring section42 to write them into a control data register 39. Further, the controlsection 38 of the main node has a memory for storing data indicating anetwork structure (will be described later).

The instruction register 35 is a register for writing various kinds ofinstruction data generated by the control section 38 for the satellitenodes thereinto. An ID (Identifier) indicating a destination of thecommand is added to written instruction data. The control data register39 is a register for writing control data generated by the controlsection 38 to control the receiving and transferring section 42thereinto. Further, a response register 40 is a register for writingvarious kinds of response data included (or contained) in the satellitepacket received by the receiving and transferring section 42 thereinto.Further, a state information register 41 is a register for writingvarious kinds of state information such as confirmation of packetreception in the receiving and transferring section 42 thereinto.

The operator 43 is used to change a value of a parameter to control anoperation (signal processing) of the main node itself, to change a valueof a parameter to remotely control an operation (signal processing) ofthe satellite nodes, or to instruct switching of a screen on the displaysection 44. When the operator 43 is operated, the operation and/oroperation amount is detected, and data indicating the operated operatorand data indicating the detected operation and/or operation amount aresupplied to the control section 38. The display section 44 is a displayfor displaying various kinds of information on the basis of control ofthe control section 38. A setting state of a desired parameter of themain node and/or other node and a network structure of the audio networksystem to which the main node is connected are displayed on the displaysection 44.

The receiving and transferring section 42 operates on the basis ofvarious kinds of control data set in the control data register 39. Whenthe satellite packet transmitted by the satellite node is received, thereceiving and transferring section 42 extracts response data from thesatellite packet to write them into the response register 40, or towrite various data such as confirmation of the packet reception into thestate information register 41. In this regard, when the main nodeoperates as a main node, transfer of a packet is carried out. A secondselector 45 is connected to the two ports 30 a, 30 b in accordance withan instruction from the receiving and transferring section 42, selectsany one output of the ports 30 a, 30 b, and outputs the fact to thereceiving and transferring section 42. When the main node operates as amain node, the main node is controlled to select an output of the port,which first receives a satellite packet in each satellite packet period,of the ports 30 a, 30 b.

When a plurality of main nodes exist on the audio network system asshown in FIG. 2, only one main node operates as a main node, and theothers operate as a satellite node. In the case where the main nodeoperates as a satellite node, each portion of the main node shown inFIG. 5B operates in the same manner as each portion corresponding to thesatellite node shown in FIG. 5A. In the case where the main nodeoperates as a satellite node, in FIG. 5B, the response register 40becomes an “instruction register” to hold various kinds of instructiondata extracted from the received main packet, and the instructionregister 35 becomes a “response register” to hold various kinds ofresponse data against the instruction data. The main packet generatingand transmitting section 34 becomes a “satellite packet generating andtransmitting section (S packet generating and transmitting section)” togenerate and transmit a satellite packet including the response data ofthe “response register” (the instruction register 35) under control ofthe control section 38. The second selector 45 then selects an output ofan M port of the ports 30 a and 30 b for the main packet period, andselects an output of an S port for the satellite packet period. Further,the first selector 36 basically selects an output of the receiving andtransferring section 42. When a satellite packet should be transmittedfrom the first selector 36 itself, the first selector 36 selects theoutput of the “satellite packet generating and transmitting section”(main packet generating and transmitting section 34) at the timing ofthe clock signal indicating the lead of the satellite packet periodapplied from the receiving and transferring section 42. The gate 37opens all of the ports other than the M port for the main packet period,and opens only a specified port for the satellite packet period appliedfrom the receiving and transferring section 12. In this regard, in FIG.5B, each of a thin arrow inputting to the main packet generating andtransmitting section 34 and a thin arrow inputting to the first selector36 from the receiving and transferring section 42 indicates a flow ofthe clock signal indicating the lead of the satellite packet period whenthe main node operates as a satellite node.

<Explanation of Operation>

FIG. 7 is a view for explaining a detecting process of route control anda network structure (topology) for transferring packet data in the audionetwork system shown in FIG. 1 or FIG. 2, and shows an example of aconfiguration (connection status between nodes) of the audio networksystem. In FIG. 7, an audio network system constructed from one mainnode (M node) 60 and four satellite nodes (S node 0 to S node 3) 61 to64 is shown.

Hereinafter, while viewing a configuration example of the audio networksystem shown in FIG. 7, a transmission and reception operation of apacket carried out in each node, a process related to route controlbetween nodes and a process related to detection of a network structure(topology) will be described.

FIG. 7A shows a state before route selection in which connecting wirebetween nodes is drawn with dotted lines, and shows that these areunconfirmed connecting wire. At this state, the main node 60 never knowsa network structure (topology) of the audio network system to which themain node 60 itself is connected. Further, in each of satellite nodes 61to 64, it is not determined whether any of four ports “port number 0(P0)” to “port number 3 (P3)” that each satellite node has becomes an Mport.

FIG. 8 is a flowchart for explaining a base process carried out by thecontrol section 38 of the main node and the control section 17 of thesatellite node. This process starts when the audio network system isturned on (when the main node and the satellite node are turned on). AtStep S1, a predetermined initializing process is carried out, wherebyvarious tasks are activated. Then, detection of various kinds of eventssuch as an operation detecting event of the operator is carried out(Step S2). Whenever any event is detected (“YES” at Step S3), a processaccording to the generated event is carried out (Step S4).

<Transmission of Main Packet>

In the control section 38 of the main node, a task to transmit the mainpacket toward the satellite nodes and the like are included in varioustasks activated by the initializing process at Step S1. FIG. 9 is aflowchart showing an example of a main packet generating andtransmitting process carried out by the main packet generating andtransmitting section 34 of the main node. This process is included in atask to start by the initializing process at Step S1 in FIG. 8. Further,FIG. 10 is a view for explaining operation timing of the generating andtransmitting process of the main packet. In FIG. 10, a horizontal axisthereof denotes time.

In the main packet generating and transmitting section 34 of the mainnode, three buffers each of which can store audio signals of 96 samples(sample data) by eight channels are prepared. One of the three buffers(1) is utilized as a buffer for writing the audio signals of the eightchannels inputted every sampling period thereinto, another one of them(2) is utilized as a buffer for generating the main packet, and stillanother one of them (3) is utilized as a buffer for transmitting themain packet. Application of each of the buffers is not fixed, and it isin turn changed among these three kinds of application in accordancewith a situation.

The audio signals of the eight channels supplied from the external audiosource (Reference numeral 3 in FIG. 1) are respectively converted intodigital signals (samples) by the ADC 31 and taken in the ADC 31 everysampling period. The taken digital audio signals of the eight channelsare subjected to signal processing in the signal processing section 32every sampling period, and inputted into the main packet generating andtransmitting section 34 of the main node. In the main packet generatingand transmitting section 34, each of the audio signals of the eightchannels inputted every sampling period is written into the audio signalwriting buffer by 96 samples (in FIG. 10, an operation from timing T1 totiming T2). In this embodiment, a time length of a packet transmittingcycle is controlled so that the audio signal of each channel is inputtedfor 96 samples every packet transmitting cycle (one msec.).

The audio signal writing buffer is separated into a region for writingeven samples and a region for writing odd samples. When the audiosignals inputted every sampling period are written into the audio signalwriting buffer, even samples (sample number S0, S2, . . . S94) and oddsamples (sample numbers S1, S3, . . . S95) are separated and writteninto the even sample region and the odd sample region, respectively.

As shown in FIG. 10, at the time when the audio signals of 96 samplesare written into the audio signal writing buffer (timing T2 in FIG. 10),the audio signal writing buffer is converted into a main packetgenerating buffer, and a main packet generating and transmitting processshown in FIG. 9 is started. Simultaneously, a buffer used to transmitthe last main packet is converted into the audio signal writing buffer,and writing of the audio signals inputted hereinafter is carried out forthe converted audio signal writing buffer.

At Step S5, the main packet generating and transmitting section 34 addsa control signal (CTR) including a command and the like set in theinstruction register 35 or data obtained by dividing the control signalinto two to each of the even samples (sample number S0, S2, . . . S94)and the odd samples (sample number S1, S3, . . . S95), generates a setof an even sample group and the control signal (CTR) and a set of an oddsample group and the control signal (CTR), and at Step S6, adds errorcheck information (EC) to each of the sets, and generates data of themain packet for the packet transmitting cycle. The main packetgenerating and transmitting section 34 then converts the main packetgenerating buffer into the main packet transmitting buffer, and waitsuntil transmission timing of the main packet (Step S7). In this regard,at this time, there is a possibility that transmission of the last mainpacket has not been carried out yet.

The main packet generating and transmitting section 34 then adds aheader and a clock signal to data for one packet composed of the set ofthe even sample group and the set of the odd sample group attransmission timing (timing T3 of FIG. 10) of the main packet everypacket transmitting cycle (one msec.) to transmit them (Step S8). InFIG. 10, a state where the main packet generating and transmittingsection 34 waits for the transmission timing (timing T3) after the mainpacket is generated, and transmission of the main packet is started isdrawn. As described above, the clock signals are embedded in the data ofone packet every 83.3 μsec., obtained by evenly dividing the packettransmitting cycle (one msec.) into twelve, at even intervals.Therefore, at Step S8 described above, the data of the main packet aretransmitted while the clock signals are embedded at intervals (83.3μsec.) corresponding to 1/12 clock of the packet transmitting cycle (onemsec.). FIG. 10 is a view illustrating a time relation of each processof input of the audio signal, generation and transmission of the mainpacket by focusing one main packet. The same process is repeatedlycarried out every packet transmitting cycle (one msec.). Namely, each ofa series of main packets is continuously transmitted every packettransmitting cycle in accordance with the input signal.

<Route Control>

In the state before route selection in FIG. 7A, the main packet istransmitted from the main node 60 to the satellite nodes 61 to 64 by theprocess of FIG. 9 described above every packet transmitting cycle.However, at this time, in each of the satellite nodes 61 to 64, it hasnot determined whether any of the four ports “port number P0” to “portnumber P3” that each satellite node has becomes an M port yet. Namely,since a route to transfer the main packet from the main node 60 to eachof the satellite nodes 61 to 64 has not been selected, the transmittedmain packet arrives at only the satellite node 61 that is directlyconnected to the main node 60.

Thus, the control section 17 of each of the satellite nodes 61 to 64carries out the M port number setting process shown in FIG. 11 when theaudio network system is turned on (or when the network is reset) to setan M port (a port for receiving the main packet) for each satellitenode. The M port number setting process is started at initializing atStep S1 in FIG. 8 described above, and is always carried outhereinafter.

At Step S9, zero is set to a check target variable i. Then, at Step S10,the control section 17 sets the variable i to M port number data of thecontrol data register 18. The control section 17 then waits forpredetermined time with respect to the port set in the M port numberdata (port corresponding to the variable i) (Step S11), and confirms areceiving state of the main packet that is to arrive every packettransmitting cycle (Step S12). The waiting time at Step S11 is set totime for a plurality of periods of the packet transmitting cycle. Inthis embodiment, since the packet transmitting cycle is one msec., thewaiting time is set to about 4 msec., for example. In the case where themain packet is not received at the port corresponding to the variable ieven after a lapse of the predetermined time (“NO” at Step S13), thecontrol section 17 determines that the port is unsuitable for the Mport, and sets a value obtained by adding one to the variable i as a newvariable i (Step S14), and the processes after Step S10 are repeated. Asthe value of variable i is incremented by one, the port number set asthe M port number data at Step S9 is shifted by one (where, i≦4). In thecase where the variable i becomes four (“YES” at Step S15), theprocessing flow returns to Step S9 to set zero to the variable i again,and confirmation of main packet reception is carried out from the portP0. A state where the M port number data are changed in turn is called astate where the M port has not determined yet.

In the case where the main packet is received at the port correspondingto the variable i for the predetermined time (“YES” at Step S13), thecontrol section 17 determines that the port corresponding to thevariable i is suitable for the M port. By repeating the processes atSteps S11 to S13 hereinafter, a main packet receiving state is monitoredat the M port (port number i), and setting of the M port is continuedwhile reception of the main packet can be confirmed. A state where the Mport number data are fixed to one port number and are not changed iscalled a state where the M port has been determined.

This makes it possible to shift a port number (M port number) of thecheck target from the port P0 one by one in turn, and to determine theport for which periodic reception of the main packet is first confirmedas an M port.

The processes at Steps S11 to S13 are repeated after reception of themain packet is confirmed at the M port to monitor the main packetreceiving state. For this reason, in the case where reception of themain packet is lost at the M port (in the case where the route for the Mport is cut off), the processing flow branches at Step S13 to “No”, andthe M port number is shifted to a next port number in turn to checkperiodical reception of the main packet, whereby the port for whichperiodical reception of the main packet is newly confirmed can be setautomatically so as to be utilized as a new M port.

In this regard, in this embodiment, since the configuration in whicheach of the satellite nodes 61 to 64 has four ports is assumed, thevalue of judgmental standard at Step S11 is “4”. However, in the casewhere the number of ports of each satellite node is n other than 4, itis determined at Step S11 whether the check target variable icorresponds with the number of ports n (i=n).

A state where the main port of each satellite node on the audio networksystem is determined by carrying out the process of FIG. 11 will bedescribed with reference to FIG. 7. The main node 60 starts to transmitthe main packet every packet transmitting cycle in the initial stateshown in FIG. 7A (a state where any satellite node does not determine anM port). When each of the satellite nodes 61 to 64 carries out the Mport number setting process of FIG. 9, the main packet is first receivedvia the port P0 of the satellite node 61 (S node 0) connected to theport P0 of the main node 60. Therefore, the satellite node 61 determinesthe port P0 as the M port.

The satellite node 61 for which the M port is determined transfers themain packet received via this M port (port P0) from the respective Sports other than the M port to a node of its destination every packettransmitting cycle (operation of the receiving and transferring section12 in FIG. 5A). Therefore, the main packet transferred by the satellitenode 61 every packet transmitting cycle starts to arrive at thesatellite nodes 62 (S node 1) and 63 (S node 2) at the same time. Theport P1 is then determined as the M port by the M port number settingprocess in the satellite node 62, while the port P1 is determined as theM port by the M port number setting process in the satellite node 63.Since the M port number setting processes in the satellite nodes 62 and63 are carried out at independent timing of each other, determination ofthe M port in these two nodes is not always carried out at the sametime.

Since each of the satellite nodes 62, 63 in which the M port isdetermined transfers the main packet, received at the determined M portevery packet transmitting cycle, from each of the S ports, the mainpacket is to arrive at the satellite node 64 (S node 3) from both of thesatellite nodes 62 and 63 every packet transmitting cycle. Although oneport is determined as the M port in the satellite node 64 by the M portnumber setting process, in this case, whether any of the port P0 andport P2 is determined as the M port is incidentally determined on thebasis of a relation between timing when the main packet starts to arriveat each port and timing when the ports are checked in turn.

Thus, the M port of each satellite node is basically determinedautomatically in the order from an upstream side of the route (at whichthe main packet is to arrive early) by the independent M port settingprocess in each satellite node. It should be noted that whether any portof each satellite node is determined as the M port is incidentallydetermined on the basis of check timing of each port in the satellitenode and timing when the main packet starts to arrive at each port fromother nodes, and the port that exists at the shortest distance from themain node is not always determined (the shortest route is not alwaysselected).

In the case where the M port is determined in each of the satellitenodes 61 to 64, the route to transfer the main packet from the main node60 to each of the satellite nodes 61 to 64 is determined. FIG. 7B showsa state where the route is determined in which the determined M port ineach node is shown by heavy frames and connecting wire of the determinedroute is shown by heavy lines. The main packet is transferred from themain node 60 to each of the satellite nodes 61 to 64 through the routedrawn with the heavy lines. However, at this time (the time when themain node 60 does not carry out “topology detection” (will be describedlater)), the main node 60 does not recognize or detect this selectedroute. The route to transfer the main packet on the audio network systemis merely determined automatically.

In FIG. 7B, for example, in the satellite node 62 (S node 1), the portP1 connected to the port P1 of the satellite node 61 is set to the Mport. At this state, in the case where a failure occurs on the routebetween the port P1 of the satellite node 61 and the port P1 of thesatellite node 62 (for example, in the case where connection is cutoff), the satellite node 62 checks reception of the main packet in theorder from the port P2, and determines a port of the main packet forwhich periodical reception is confirmed as a new M port because the mainpacket does not arrive at the port P1 of the satellite node 62. Namely,in the case of the state of FIG. 7B, either the port P2 or the port P3is to be set to the new M port.

Thus, according to the present embodiment, even in the case where afailure occurs on a route, by means of relatively simple control tocheck the ports one by one in each satellite node and to set the portfor which reception of the main packet is confirmed to the M port, theroute can be changed automatically (dynamic routing), and the failurecan be avoided. The automatic route changing process carried out by eachsatellite node can be achieved by a simple process (M port numbersetting process) for which complex control such as generation of arouting table is not required.

Further, as shown in FIG. 2 described above, in the case of the networkstructure having a plurality of main nodes (a configuration in whichmain nodes are multiplexed), only one of the plurality of main nodesoperates as the main node (main operation), and the others operate asthe satellite node (satellite operation). Therefore, the main node thatcarries out the satellite operation carries out the M port numbersetting process, and the M port (port at which the main packet isreceived) is set. FIG. 12 is a flowchart showing an M port numbersetting process carried out by the control section 38 of the main nodethat carries out a satellite operation. This M port number settingprocess is started at the initializing at Step S1 in FIG. 8 describedabove, and is always carried out hereinafter. In the M port numbersetting process carried out by the control section 38 of the main nodethat carries out the satellite operation, a process of switching theoperation of the main node from the satellite operation to the mainoperation is included. In this regard, in the process of FIG. 12, it isassumed that the main node has a configuration with two ports (P0, P1).

At Step S100 in FIG. 12, the control section 38 sets each of checktarget variables i, j to zero. Here, the variable j is a port number ofthe port in which reception of the main packet is finally detected,while the variable i is the number of checks from the time whenreception of the main packet is not detected. At Step S101, the controlsection 38 then sets a value of a formula mod[(i+j)/2] as the M portnumber data of the control data register 39. The formula mod[(i+j)/2] isa function for obtaining a remainder of division “(i+j)/2”. Adenominator “2” in a square bracket is the number of ports with whichthe main node is provided. In the case where the number of ports is nother than two, the port number is obtained by the formula mod[(i+j)/n].In the case where each of the variables i, j is zero, the M port numberdata (a value of the formula mod[(i+j)/2]) become “0”. Therefore, it ispossible to start checks in ascending order of the port numbers.

The control section 38 waits for predetermined time (Step S102) withrespect to the port number (mod[(i+j)/2]) set to the M port number data,and confirms the receiving state of the main packet (Step S103). Here,the waiting time of Step S102 may be the same as the waiting time ofStep S12, or may be different from the waiting time of Step S12. In thecase where the main packet is not received at the check target port evenafter a lapse of the predetermined time (“NO” at Step S104), it isdetermined that the port corresponding to the value of the formulamod[(i+j)/2] is unsuitable as the M port. At Step S105, a value obtainedby adding one to the variable i is set to a new variable i, and theprocesses after Step S101 are repeated. In the case where a value of thevariable i is incremented by one, the port number (mod[(i+j)/2]) isshifted by one in the port numbers (in this case, “0” and “1”) of theports that the main node has.

In the case where the main packet is received at the check target portin the predetermined time (“YES” at Step S104), the control section 38determines that the port (port number=mod[(i+j)/2]) is suitable as the Mport. At Step S106, the control section 38 sets the formula mod[(i+j)/2](current M port number) to the variable j, and sets “0” to the variablei. Then, by repeating the processes after Step S102, the main packetreceiving state is monitored at the M port (port number=mod[(i+j)/2]),and setting of the M port is continued while reception of the mainpacket can be confirmed.

In the case where reception of the main packet is lost at the M port (inthe case where the route for the M port is cut off), the processing flowbranches at Step S104 to “No”, at Step S105, a value obtained by addingone to the variable i is set to a new variable i, and the processesafter Step S101 are carried out. At Step S105 described above, theformula mod[(i+j)/2] (current M port number) is set to the variable j,and “0” is set to the variable i. Therefore, the M port number(mod[(i+j)/2]) newly set at Step S101 becomes a next port number of thelast M port number. Namely, in the case where the last M port number isP0, the newly set M port number becomes P1. In the case where the last Mport number is P1, the newly set M port number becomes P1. By shiftingthe check target port in turn, the port for which reception of the mainpacket is first confirmed is set to the M port.

Namely, the M port number setting process carried out at the main nodethat carries out the satellite operation is similar to the M port numbersetting process of the satellite node shown in FIG. 11 in that the checktarget port is shifted one by one to confirm reception of the mainpacket, the port is continuously set to the M port while reception ofthe main packet is confirmed, and in the case where reception of themain packet is lost, the M port number is shifted to a next port numberin turn to check periodical reception of the main packet and the portfor which the periodical reception of the main packet is newly confirmedis set as a new M port.

In the processes of FIG. 12, in the case where a value of the variable ibecomes a predetermined value k (“YES” at Step S107), a process toswitch an operation of the main node from a satellite operation to amain operation is carried out at Steps 5108 and S109. This predeterminedvalue k is a value set as a standard for determining whether each mainnode is caused to start the main operation or not. When thedetermination that a main node is “unsuitable as the M port” is made forthe kth times in a row, the main node starts a main operation. Since ineach main node its ports should be checked at least through the ports,the predetermined value k is set to a value equal to or more than thenumber of ports that each main node itself has. When route selection isnot terminated yet (FIG. 7A, when the audio network system is turned onor when the network is reset), the predetermined value k may be adifferent value for each main node so that route selection is carriedout without problems even though each main node starts the M port numbersetting task at about the same time. Then, after the route has beenselected once (FIG. 7B), the predetermined value k may be the untouchedvalue, or may be changed so as to become the same value between the mainnodes.

Since zero is set to the variable i at the process start (Step S100) andzero is set to the variable i after the M port is determined (StepS105), the value of the variable i becomes k only in the case where thetwo ports P0 and P1 are checked total kth times and as a resultreception of the main packet has never detected, in other words, only inthe case where the processing flow branches at Step S104 to “No” kthtimes in a row. Therefore, in the case where the value of the variable ibecomes k (“YES” at Step S107), the control section 38 of the main nodedetermines that there is no main node that carries out the mainoperation on the audio network system, stops various tasks for thesatellite operation (Step S108), and activates various tasks for themain operation (Step S109).

Thus, even though the main node that carries out the main operationdisappears on the audio network system, the main node that carried outthe satellite operation (substantial satellite node) is automaticallyswitched to a main node that carries out the main operation, and takesover the tasks such as transmission of the main packet. Therefore, it ispossible to continue the operations of the audio network system.

<Transfer of Packet>

Next, an operation of packet transfer in the satellite node to which theM port is set and an operation of reception of the main packet (audiosignal) will be described. In this regard, although the operationcarried out by the satellite node will be described here, the main nodealso carries out the same operation while the main node carries out thesatellite operation.

FIG. 13 is a flowchart for explaining an operation of the receiving andtransferring section 12 (operation of hardware) when it is notified tostart to receive the main packet or satellite packet by the receptiondetecting signal (dotted line in FIG. 5A) in the satellite node. At StepS16 in FIG. 13, the receiving and transferring section 12 determineswhether a kind of packet started to receive is a main packet (M packet)or a satellite packet (S packet). Timing when start of reception of apacket is detected is a main packet period. In the case where the startof reception is notified at the M port by the reception detectingsignal, the receiving and transferring section 12 causes the selector 11to select the M port, and receives the main packet received at the Mport. Here, a current M port is determined by the M port number data setto the control data register 18. In this case, the processing flowbranches at Step S16 to “M packet”. At Step S17, the receiving andtransferring section 12 opens the gate 14 for all ports (S ports) otherthan the M port, and at Step S18, the receiving and transferring section12 starts to transfer the currently receiving main packet from the leadthereof while receiving the main packet. Thus, the main packet istransferred from each S port toward a downstream side of the route.

Further, in the case where timing to detect reception of the packet is asatellite packet period and start to receive at any one S port isnotified by the reception detecting signal, the receiving andtransferring section 12 causes the selector 11 to select the S port, andreceives the satellite packet received at the S port. In this regard, itis not supposed to notify start of reception at a plurality of S portsfor one satellite packet period in view of system design. However, inthe case where start of reception at a plurality of S ports is notifiedunder some kinds of circumstances, the selector 11 is caused to selectthe S port for which start of reception is first notified from the Sports, and receives only the satellite packet from the selected S port.At Step S19, the receiving and transferring section 12 checks whetherthe S port for which the start of reception is notified is set toprohibition of transfer or not on the basis of the prohibited port dataof the control data register 18. It will be described later in what casea port is set to prohibition of transfer. In the case where the S portis not set to prohibition of transfer (“NO” at Step S19), at Step S20,the receiving and transferring section 12 opens the gate 14 of the Mport. A current M port number is determined on the basis of the M portnumber data set to the control data register 18. At Step S21, thereceiving and transferring section 12 starts to transfer the receivedsatellite packet from the lead thereof. Thus, the main packet istransferred from the M port to an upstream side of the route.

<Reception of Main Packet (Reproduction of Audio Signal)>

FIG. 14 is a flowchart for explaining an operation (operation ofhardware) of the receiving and transferring section 12 when reception ofthe main packet by a packet transmitting cycle (one msec.) is completedin the satellite node. Further, FIG. 15 is a view for explainingoperation timing of the process to receive a main packet by a packettransmitting cycle (one msec.) and to reproduce audio signals (96samples) in the received main packet. In this regard, a horizontal axisin FIG. 15 denotes time. Further, two buffers (large) capable of storingaudio signals of 96 samples (sample data) for eight channels and twobuffers (small) capable of storing them for one channel are prepared inthe receiving and transferring section 12 of the satellite node. One ofthe two buffers (large) of the former is (1) utilized as a buffer forreceiving a main packet, and the other is (2) utilized as a buffer fordata check of the received main packet. Further, one of the two buffers(small) of the latter is (1) utilized as a buffer for writing the audiosignal (sample) extracted from the main packet, and the other is (2)utilized as a buffer for reproducing the extracted audio signal.Application of each of the buffers (large) and the buffers (small) isnot fixed, and it is changed in turn between the corresponding two kindsof application in accordance with the situation.

In FIG. 15, the receiving and transferring section 12 starts to receivethe main packet via the M port every packet transmitting cycle (onemsec.) (timing T4 in FIG. 15), and stores data on the main packet everypacket transmitting cycle (one msec.) in the main packet receivingbuffer from the lead thereof. The data of the main packet every packettransmitting cycle (one msec.) correspond to the “Data 1” to “Data 11”of FIG. 3, and are composed of audio signals of eight channels for 96samples and control signals.

In the data of the main packet every packet transmitting cycle (onemsec.), as explained with reference to FIG. 3, 12 clock signals areembedded every 83.3 μsec. Therefore, the receiving and transferringsection 12 detects reception timing of each clock signal received every83.3 μsec., and transmits the reception timing of each clock signal tothe oscillator (OSC) 22. It is described above that the OSC 22synchronizes with the reception timing of each clock signal to generatea sampling clock (96 kHz), and the sampling clock synchronized with thesampling clock of the main node is reproduced.

At the time when reception of the main packet every packet transmittingcycle (one msec.) is completed (timing T5 in FIG. 15), the process ofFIG. 14 is started. The receiving and transferring section 12 switchestheir roles between the receiving buffer and the data check buffer, andcarries out an error check for each of data on a first-half portion ofthe main packet and data on a second-half portion of the main packet andrecovery of the data in the case where an error is detected (ifpossible) on the basis of error check information (EC) on the mainpacket, whose reception is completed, in the data check buffer. Then,the receiving and transferring section 12 extracts the audio signal ofone channel indicated by the reception channel number data set in thecontrol data register 18 for 96 samples from the packet to write it intothe writing buffer, and extracts the command (control signal CTR)included in the same packet to write it into the instruction register 15(Step S22 in FIG. 14).

As explained with reference to FIG. 3, the data of one main packet(“Data 1” to “Data 11”) are composed of two parts including a set of theeven sample group, the control signal and the error check informationand a set of the odd sample group, the control signal and the errorcheck information. Since the data of the main packet are received fromthe header portion in turn, the set of even sample group and the set ofodd sample group are separated into the first-half portion and thesecond-half portion of the received main packet, respectively. Namely,the error check for “the first-half portion and the second-half portionof the main packet” is to check an error of the sample group of the evensample group (that is, sample group of even samples) using the errorcheck information added to the even sample group, and to check an errorof the sample group of the odd sample group (that is, sample group ofodd samples) using the error check information added to the odd samplegroup. In the error check for each group, in the case where the data inwhich an error occurs are small even when the error is detected, thedata can be recovered on the basis of the error check information.Therefore, not only in the case where no error is detected in a group,but also in the case where data of a portion can be recovered even whenan error is detected in the portion, the data of the group can beutilized (OK). Hereinafter, “OK” cases including this case are expressedas “there is no error”. On the other hand, in the case where an error isdetected in a group and the data cannot be recovered, the data of thegroup cannot be utilized (NG), and therefore, it is expressed “there isan error”. In this regard, although the error check based on the errorcheck information is fundamental, a function of data recovery may not benecessary and be an option.

As a result of the error check, in the case where there is no error inboth the first-half portion and the second-half portion (even samplegroup and odd sample group) of the main packet (“YES” at Step S23), atStep S24, successive 96 samples are generated by alternately placing(arranging) the first-half portion and the second-half portion (evensample group and odd sample group) of the main packet one sample by onesample, and the receiving and transferring section 12 waits untilreproduction timing.

Then, at Step S25, after the 96 samples (the audio signals generatedfrom the data of the main packet in the last packet transmitting cycle(last one msec.)) are currently reproducing from the reproducing buffer,the 96 samples (the audio signals generated from the data of the mainpacket in the packet transmitting cycle) generated at Step S24 andwritten into the writing buffer are synchronized with the sampling clockgenerated by the OSC 22 to reproduce them. More specifically, at thetiming to reproduce the 96 samples (timing T6 in FIG. 15), the currentwriting buffer is converted into a reproducing buffer, the currentreproducing buffer is converted into a writing buffer, and the 96samples of the new reproducing buffer are outputted one sample by onesample every sampling period indicated by the sampling clock generatedby the OSC 22.

On the other hand, as a result of the error check, in the case wherethere is an error in any one of the first-half portion and thesecond-half portion (even sample group and odd sample group) of the mainpacket (“NO” at Step S23, and “YES” at Step S26), at Step S27, the 48samples of the group (even sample group or odd sample group) of thesamples in which there is no error are subjected to twice oversampling,whereby the successive 96 samples are generated using only the samplegroup of one group and are written into the writing buffer. Then, at thetiming T6 to be reproduced, the successive 96 samples generated at StepS27 are reproduced (Step S25).

Thus, even in the case where there is an error in any one of the evensample group (i.e., first error) and the odd sample group (i.e., seconderror), the audio signals can be reproduced using the other group. Inthis case, a sampling frequency decreases by half and a quality of theaudio signals is somewhat deteriorated, but it is far well than the casewhere the error portion becomes “silent” due to lack of the data.

Further, as a result of the error check, in the case where there areerrors in both the first-half portion and the second-half portion (evensample group and odd sample group) of the main packet (“NO” at Step S23,and “NO” at Step S26), at Step S28, the reproducing audio signals fadeout from the reproducing buffer, and silent 96 samples (i.e., “silentaudio signals”) are written into the writing buffer in place of thesamples received at the packet transmitting cycle (mute sound), or thereproducing 96 samples in the reproducing buffer are written into thewriting buffer as they are or after attenuation (repeat sound). Then, atthe timing T6 to be reproduced, the 96 samples of mute sound or the 96samples of repeat sound are reproduced (Step S25).

In this regard, the flowcharts of FIGS. 13 and 14 described above areones for explaining the operation when start of the reception of themain packet is detected at one packet transmitting cycle and theoperation when reception of the main packet is completed, respectively.For this reason, they are drawn so that the process is terminated by oneloop. In fact, since reception of the main packet is detected everypacket transmitting cycle (one msec.) and reception of the main packetis completed every packet transmitting cycle (one msec.), each of theoperations shown in FIGS. 13 and 14 is repeated every packettransmitting cycle (one msec.).

As described above, although this embodiment is described with referenceto FIGS. 9 to 15, this is an operation immediately after transmission,reception and transfer of the main packet and route control (setting ofthe M port in each satellite node) required for transfer of the mainpacket in the audio network system according to this embodiment.

<Topology Detection>

In a state immediately after the route selection shown in FIG. 7B(setting of the M port in each of the satellite nodes), a route totransfer the main packet is merely selected, and the main node 60delivers the audio signals to the satellite nodes by means of theperiodically transmitted main packet. However, since the main node 60does not recognize the network structure (topology), that is, whichroute any satellite node is connected to, the main node 60 cannotspecify any satellite node separately and remotely control it.

Hereinafter, a network structure (topology) detecting process and aconnection confirming process carried out by the main node 60 will bedescribed. By carrying out the network structure (topology) detectingprocess and the connection confirming process periodically, the mainnode 60 can generate data indicating a network structure (topology) anddynamically recognize the network structure (topology). In this regard,the word “topology” in this specification indicates all of the mainnodes and the satellite nodes and connecting wire functioning as routesto transfer a main packet in the audio network system in which the mainnodes and the satellite nodes are physically connected to each other bymeans of the cables (connecting wire). Further, the connecting wire thatis not utilized as a transmission route of a main packet of theconnecting wire in the audio network system is called “spare wire”. Inthis regard, in the detection of the topology, the main node thatcarries out a satellite operation carries out the same operation as thesatellite nodes. In the explanation for this topology detection, inorder to simplify the explanation, the main node that carries out thesatellite operation is also called a satellite node.

FIG. 16 is a view for explaining transition of the network structuredata according to progress of the topology detecting process and theconnection confirming process. In FIG. 16, a network corresponds to theaudio network system shown in FIG. 7 (network system constructed fromone main node 60 and four satellite nodes 61 to 64). FIG. 16A is thecontent of a state immediately after the route selection (before thetopology detecting process). At this state, the main node 60 merelyunderstands that the main node 60 itself exists (ID=A) and has two ports(P0 and P1), topology of destinations of the P0 and P1 is unconfirmed(in FIG. 16, topology unconfirmed is indicated by a mark “*”).Hereinafter, a state where topology is detected through the topologydetecting process will be described.

FIG. 17 is a flowchart showing an example of a topology detectingprocess carried out by the control section 38 of the main node 60. Thisprocess is a process periodically carried out by the control section 38of the main node 60 every predetermined timing, and runs in thebackground separately from a main operation of the main node 60(transmission of a main packet (audio signals)).

At Step S29, the main node 60 generates a transfer prohibiting commandto instruct all S ports, which each of the nodes has, to prohibittransfer of a satellite packet, adds a broadcast ID to the transferprohibiting command (here, the command is addressed to all nodesincluding unknown node(s)), and transmits it with a main packet. Each ofthe satellite nodes 61 to 64 that receive the main packet including thistransfer prohibiting command extracts the transfer prohibiting commandfrom the main packet to set it to the instruction register 15.

FIG. 18 is a flowchart showing an example of a process carried out bythe control section 17 when the control section 17 of each of thesatellite nodes 61 to 64 receives the transfer prohibiting command fromthe instruction register 15. The control section 17 of each of thesatellite nodes 61 to 64 compares the ID added to the transferprohibiting command with its own ID to check whether the command isaddressed to the satellite node itself. In the case where the transferprohibiting command is addressed to the satellite node itself (“YES” atStep S43), the control section 17 sets prohibited port data forprohibiting transfer of a satellite packet for the port specified by thetransfer prohibiting command to the control data register 18 (Step S44).The prohibited port data are also data for permitting transfer of asatellite packet for ports that are not specified. The broadcast ID toset all nodes to the destination is added to the transfer prohibitingcommand transmitted at Step S29, and the transfer prohibiting command isa command for prohibiting transfer of a satellite packet for all Sports. For this reason, the control section 17 of each of the satellitenodes 61 to 64 sets the prohibited port data for prohibiting transfer ofa satellite packet for all S ports (three ports other than M port) ofthe satellite node to the control data register 18. In this case, sincetransfer of a satellite packet is prohibited here, the main packettransmitted from the main node 60 can be transferred continuously.

At Step S30 in FIG. 17, the main node 60 transmits the main packetincluding an existence confirming command to all of the satellite nodes61 to 64, and confirms whether there is a reply of the satellite packetincluding an existence confirming response from any satellite nodeseparately for each of the two ports P0, P1. This existence confirmingcommand is a command transmitted to confirm a node connected to a portin the case where the connected node is unknown. Thus, an ID of the nodefor the destination cannot be identified. Therefore, a broadcast ID isalways added to the existence confirming command. In the main node 60having a plurality of ports, the main packet including the sameinstruction data is transmitted from all of the ports at the same time.Since the main packet including the same existence confirming command istransmitted from both of the ports P0, P1 at the same time at Step S30,the satellite packet including the existence confirming response isreplied from each of both of the ports if the satellite nodes arerespectively connected to both of the ports. For that reason, here, themain node 60 selects any one of the ports P0, P1 by the selector 45 inadvance to send the existence confirming command via the selected port,and selectively receives the satellite packet from the port so as toseparately confirm the existence confirming response.

The receiving and transferring sections 12 of all of the satellite nodes61 to 64 receive the existence confirming command broadcasted from themain node 60, and write the received existence confirming command intothe instruction registers 15, respectively. FIG. 19 is a flowchartshowing an example of a process carried out by the control section 17 ofeach of satellite nodes 61 to 64 when the control section 17 receivesthe existence confirming command from the instruction register 15. Thecontrol section 17 of each of the satellite nodes 61 to 64 confirmswhether a “response prohibiting command” against the existenceconfirming command is set to the instruction register 15 of thesatellite node or not at Step S45. The “response prohibiting command”will be described later. At the present stage, all of the satellitenodes 61 to 64 are not set to prohibition of a response (“NO” at StepS45). The control section 17 of each of the satellite nodes 61 to 64generates existence confirming response data including the ID of thesatellite node and port information (information on the number of portsand an M port number) (Step S46), generates a satellite packet on thebasis of the generated existence confirming response data, and sets upso as to transmit the satellite packet from the M port (Step S47). Morespecifically, an instruction to transmit the satellite packet from the Mport corresponding to the M port number of the control data register 18and the generated existence confirming response are set to the responseregister 19.

FIG. 20 is a flowchart showing a satellite packet transmitting operationcarried out by the receiving and transferring section 12 when aninstruction to transmit a satellite packet is set to the responseregister 19 by the control section 17 of the satellite node. Thereceiving and transferring section 12 waits for timing to transmit thesatellite packet (timing of the clock signal indicating the lead of thesatellite packet period) (Step S48). When it becomes the transmissiontiming, the receiving and transferring section 12 opens the gate 14 ofthe packet transmitting port (the M port set at Step S47 describedabove) set to the response register 19 (Step S49), causes the satellitepacket generating and transmitting section 20 to generate a satellitepacket on the basis of the data of the response register 19, andtransmits the generated satellite packet from the packet transmittingport set to the response register 19 (Step S50). Thus, the satellitepacket including the existence confirming command is transmitted fromthe M port.

Returning to FIG. 17, at this stage (stage at Step S30), all of thesatellite nodes 61 to 64 that receive the existence confirming commandreply the existence confirming response. However, since prohibition oftransfer of the satellite packet is set to all S ports of all of thesatellite nodes 61 to 64 at Step S29 as described above, an existenceconfirming response of each of nodes other than the satellite nodesdirectly connected to the ports P0, P1 of the main node 60 is nottransferred. Therefore, in the configuration example of the audionetwork system shown in FIG. 7, only a reply from the M port P0 of thesatellite node 61 connected to the port P0 of the main node 60 arrivesat the main node 60.

When the satellite packet including the existence confirming response isreceived from the satellite node (“YES” at Step S31), the main node 60additionally records the ID (=B) of the satellite node 61 and portinformation of the node from the satellite packet in the networkstructure data (Step S32).

FIG. 16B shows the content of the network structure data at the timewhen the port P0 of the main node 60 is checked and the satellite node61 (S node 0) is discovered. At this state, in the network structuredata, the fact that the M port P0 of the satellite node 61 (ID=B) isconnected to the port P0 of the main node 60 (the content of“destination ID” and “port” fields for “M node A” and “P0”) is recorded,the ID (=B) of the satellite node 61 and port information of thesatellite node 61 (information on the number of ports and the M portnumber) are additionally recorded, and further, the fact that the P0 ofthe main node 60 (ID=A) is connected to the P0 of the satellite node 61(in FIG. 16, the content of “destination ID” and “port” fields for “Snode 0” and “P0”) is written.

In this regard, in FIG. 16, information on the M port number is recordedby a master port flag “M” set to each port of each node. The master portflag “M” is a two-valued flag indicating that the port is the M port by“1” and indicating that the port is the other ports (S ports) by “0”.Moreover, “topology unconfirmed” (indicated by a mark “*” in FIG. 16) isrecorded in the destination ID field for each of three S ports of thesatellite node 61 (ID=B). Further, the master port flag “M” for theports P0, P1 of the main node 60 becomes “no value”.

Further, in the configuration example of the audio network system shownin FIG. 7, since no node is connected to the port P1 of the main node60, no existence confirming response is returned from the port P1 of themain node 60. Thus, the content of the network structure data aftercheck of the port P1 of the main node 60 becomes as shown in FIG. 16C.At this time, since the main node 60 carries out only confirmation oftopology, that is, confirmation of a portion through which the routepasses, it is unconfirmed whether any node is connected to the port P1or not. Therefore, as shown in FIG. 16C, “destination unconfirmed”(indicated by a mark “**” in FIG. 16) is recorded in the destination IDfield for the P1 of the M node A in the network structure data.

In this regard, in the case where the main node 60 does not receive anysatellite packet including an existence confirming response from anysatellite node via any port (“NO” at Step S31), it is determined thatthere is no connection of the satellite nodes to the main node 60 (StepS33), and the topology detecting process is terminated.

At Step S34, the control section 38 of the main node 60 selects one ofthe S ports of topology unconfirmed in the network structure data to anS port XSP for a check target. In a state after check of each of theports P0, P1 of the main node 60 (state shown in FIG. 16C), since all ofthe three S ports P1 to P3 of the satellite node 61 are “topologyunconfirmed”, one of these is selected as the XSP. The selection of theXSP is carried out in the order of port number. Namely, the S port P1 ofthe satellite node 61 is first selected as the XSP.

At Step S35, the main node 60 transmits a transfer prohibiting commandwith the main packet to prohibit transfer of a satellite packet for allS ports other than the following S ports to each of the satellite nodesin turn so as to permit transfer of the satellite packet for only the Sport selected as the XSP and the respective S ports on a transmissionroute (hereinafter, referred to as “the route”) of the main packet fromthe main node 60 to the S port. “The route” is also a route on which thesatellite packet received at the port XSP goes through until thesatellite packet arrives at the main node 60.

In the case where the XSP is the S port P1 of the satellite node 61 andthe satellite packet received at the S port P1 of the satellite node 61is to be transferred, the packet is sent out from the M port P0 of thesatellite node 61, and directly arrives at the main node 60. For thisreason, there is no “S port on the route”. Therefore, at this stage, thecontrol section 17 of the satellite node 61 rewrites the prohibited portdata of the control data register 18 for only XSP=the S port P1 of thesatellite node 61 into permission to transfer a satellite packet inaccordance with the command at Step S18. Therefore, all S ports of allof the satellite nodes other than the S port P1 of the satellite node 61are prohibited from transferring a satellite packet.

Further, at Step S36, the main node 60 transmits a response prohibitingcommand, with the main packet, to instruct prohibition of a response tothe existence confirming command to each of the satellite nodes on “theroute” in turn. Since existence of each of the satellite nodes on “theroute” has already been confirmed and the ID has been turned out, it ispossible to transmit the command addressed to the satellite node(command to which the ID of the satellite node is added).

FIG. 21 is a flowchart showing an example of a process carried out bythe control section 17 of each of the satellite nodes 61 to 64 when thecontrol section 17 receives a response prohibiting (or permitting)command from the instruction register 15. The control section 17compares the ID added to the response prohibiting (or permitting)command with its own ID to check whether or not the command is addressedto the satellite node itself. In the case where the response prohibiting(or permitting) command is addressed to the satellite node (“YES” atStep S51), prohibition (or permission) of the response to the existenceconfirming command is set in the control data register 18 (Step S52).

When the XSP is the S port P1 of the satellite node 61, a “satellitenode on the route” is only the satellite node 61 itself. Therefore, onlythe satellite node 61 cannot respond to the existence confirming command(generation and transmission of a packet of the existence confirmingresponse) by the process at Step S36 in FIG. 17.

At Step S37 in FIG. 17, the main node 60 transmits the main packetincluding the existence confirming command to all of the satellite nodes61 to 64, and confirms presence or absence of a reply of the satellitepacket including the existence confirming response from the satellitenode.

All of the satellite nodes 62 to 64 except for the satellite node 61that is prohibited from responding respond to the existence confirmingcommand transmitted from the main node 60. However, since permission oftransfer of the satellite packet is set to only the S port P1 of thesatellite node 61 at Step S35 as described above, only the satellitepacket received at the S port P1 by the satellite node 61 is sent outfrom the M port P0 of the satellite node 61, and arrives at the mainnode 60. Therefore, in the configuration example of the audio networksystem shown in FIG. 7, only the existence confirming responsetransmitted from the node connected to the S port P1 of the satellitenode 61, that is, the satellite node 62 (S node 1) arrives at the mainnode 60.

When the existence confirming response is received (“YES” at Step S38),the main node 60 records information on the destination for the checktarget port XSP of the network structure data on the basis of thereceived existence confirming response (Step S39). Namely, thecontention of the S port P1 of the satellite node 61 (S node 0), thatis, the “destination ID=C (satellite node 62)” and the “port number=P1”is written into the network structure data. Further, in the case wherethe satellite node 62 for the destination is first detected, the ID ofthe satellite node (S node 1) 62 (=C) and the port information(information on the number of ports and the M port number) areadditionally recorded in the network structure data on the basis of thereceived existence confirming response, and the fact that the port “P1”of the “S node 1” additionally recorded is connected to the check targetport XSP (the content of the “destination ID=B” and the “portnumber=P1”) is written into the network structure data.

FIG. 16D shows the content of the network structure data immediatelyafter the S port P1 of the satellite node 61 is checked. At this state,the main node 60 recognized that the S port P1 of the satellite node 61is connected to the M port P1 of the satellite node 62, and that thereare topology unconfirmed S ports P0, P2 and P3 in the satellite node 62.

In the case where there is a topology unconfirmed S port (one indicatedby the mark “*”) on the network structure data, the main node 60 returnsthe process to Step S34 (“YES” at Step S41), and hereinafter, the mainnode 60 carries out the processes in the same manner. The check iscarried out every one check target port XSP.

FIG. 16E shows the content of the network structure data immediatelyafter the S ports P2, P3 of the satellite node 61 are checked after thecheck of the S port P1 of the same satellite node 61. When the S port P2of the satellite node 61 is selected as the XSP, at Step S35, only the“S port P2 of the satellite node 61” and the S ports on the route arepermitted to transfer a satellite packet, and the satellite node 61 isprohibited from responding to an existence confirming command.Therefore, the existence confirming command is returned to the main node60 from only the satellite node 63 (S node 2, ID=D) whose M port isconnected to the S port P2 of the satellite node 61. Thus, the main node60 recognized that the M port P1 of the satellite node 63 (S node 2,ID=D) is connected to the S port P2 of the satellite node 61, and thatthere are topology unconfirmed S ports P0, P2 and P3 in the satellitenode 63 (S node 2, ID=D).

Further, when the S port P3 of the satellite node 61 is selected as theXSP, at Step S35, only the “port P3 of the satellite node 61” and the Sports on the route are permitted to transfer a satellite packet, and thesatellite node 61 is prohibited from responding an existence confirmingcommand. Therefore, the existence confirming response is not returned tothe main node 60 (“NO” at Step S38). Since the main node 60 merelyconfirms the topology, the main node 60 does not confirm whether anynode is connected to the P3 of the satellite node 61 or not. Therefore,as shown in FIG. 16E, “destination unconfirmed” (indicated by a mark“**” in FIG. 16) is recorded in a destination ID field for the port P3of the satellite node 61 (S node 0) in the network structure data.

The main node 60 carries out the processes at Step S34 to Step S41 untilany topology unconfirmed S port (one indicated by the mark “*”)disappears on the network structure data to check all S ports of all ofthe satellite nodes (S node 0, 1, 2) 61 to 64 on the audio networksystem shown in FIG. 7 one by one in turn. Thus, the main node 60 candetect all of the satellite nodes 61 to 64 that exist on the audionetwork system and the connecting wire (route) utilized to transfer amain packet and a satellite packet between nodes. The main node 60 candetect topology (network structure) shown with the solid lines in FIG.7B (dotted-line portions in FIG. 7B are not detected).

FIG. 16F shows the content of the network structure data after all Sports of all of the satellite nodes (S node 0, 1, 2, 3) 61 to 64 arechecked. The main node 60 carries out management and control of theaudio network system on the basis of the network structure data for allports of all of the satellite nodes (S node 0, 1, 2, 3) 61 to 64, whichare generated by the topology detecting process. More specifically, itis possible to display the detected topology on the display section 44,to monitor an operation state of each satellite node included in thetopology, and to remotely control each of the satellite nodes.

In this regard, a concrete example of “the route” at Step S35 describedabove will be described. For example, in the case where the S port P0 ofthe satellite node 62 (S node 1) is set to the XSP, the satellite nodeon “the route” is the satellite node 61 (S node 0), and the S port on“the route” is the S port P1 of the satellite node 61. “The route” isturned out by referring to the network structure data, and tracking theroute to the upstream side in turn from the satellite node having theXSP as a starting point, an M port of the satellite node→connectingwire→an S port of a next satellite node→an M port of the satellitenode→connecting wire . . . until arrival of the main node 60.

In the case where a topology check for all S ports of all of thesatellite nodes (S node 0, 1, 2, 3) 61 to 64 is terminated (“NO” at StepS41), the main node 60 generates a transfer permitting command forpermitting to transfer the received satellite packet for all S portsthat the node has, adds a broadcast ID thereto, and transmits it withthe main packet (Step S42). When this command is received, the controlsection 17 of each of the satellite nodes 61 to 64 sets prohibited portdata for permitting its own all S ports (three ports other than the Mport) to transfer the satellite packet to the control data register 18.This is because in order to remotely control each of the satellite nodes61 to 64 by the main node 60, it is inconvenient unless permission totransfer a satellite packet is set to each S port of each of thesatellite nodes 61 to 64.

By carrying out the topology detecting process described above, the mainnode 60 can detect topology of the audio network system by means of asimple communication protocol (the “existence confirming command” fromthe main node, the “existence confirming response” from the satellitenode and the “satellite packet transfer prohibiting/permitting commandfor each S port” against the satellite node, and the “responseprohibiting/permitting command against each satellite node”). At thistime, each of the satellite nodes 61 to 64 may merely carry out verysimple processes (response to “existence confirming command”, remotecontrol in accordance with the transfer prohibiting/permitting command,and remote control in accordance with the response prohibiting command),and complex processes such as a process to detect neighboring nodes,which has been carried out when to generate a conventional routingtable, are not required.

This topology detecting process is suitable for application forpresenting topology (network structure) of the audio network system to auser in the main node 60. When the control section 38 of the main node60 terminates topology detection for all S ports of all of the satellitenodes (S nodes 0, 1, 2, 3) 61 to 64, it is possible to display the wholeimage of the detected topology on the display section 44 on the basis ofthe network structure data. Here, the whole image of the topologydisplayed on the display section 44 is a connection status between nodesshowing the route through which the main packet is to be transferred,shown in FIG. 7B with heavy lines. This allows the user to confirmtopology of the audio network system by means of the display screen ofthe display section 44. In this regard, a display form of the topologyto be displayed on the display screen may be a form to graphicallydisplay the topology by means of “block images” schematically indicatingthe nodes and “lines” indicating the cables, or the topology may bepresented by means of character information.

In this regard, the topology may not be displayed on the display section44 after all S ports of all of the satellite nodes (S nodes 0, 1, 2, 3)61 to 64 have been checked (after topology of the whole network isdetected). The display content on the display section 44 may be updatedwhenever topology for each S port of each of the satellite nodes 61 to64 is detected, whereby a range of the topology to be displayed may beexpanded gradually.

Further, in the case where the configuration of the audio network systemis a configuration in which main nodes are duplexed as shown in FIG. 2(configuration of an audio network system having a plurality of mainnodes), only any one of them becomes a main node, and the other nodescarry out an operation as a satellite node. Therefore, in the topologydetecting process described above, each of the main nodes that operateas a satellite node is substantially regarded as a satellite node.Namely, each S port of the main node that operates as a satellite nodeis selected as a check target port XSP for topology detection.

<Confirmation of Connection (Detection of Spare Wire)>

In the topology detecting process described with reference to FIG. 17,all of the satellite nodes 61 to 64 that exist on the audio networksystem, and connecting wire (route) utilized for transfer of the mainpacket and the satellite packet are detected. Therefore, for example, inFIG. 7B, unlike the connecting wire between the S port P2 of thesatellite node 62 (S node 1) and the S port P0 of the satellite node 63(S node 2) (connecting wire shown with dotted lines), “spare wire” thatis not utilized to transfer a main packet and a satellite packet is notdetected. At the stage that the topology detecting process isterminated, “destination unconfirmed” is recorded in the networkstructure data for each of all S ports other than the ports on the routeutilized to transfer a main packet and a satellite packet (see FIG.16F).

The control section 38 of the main node 60 carries out the “connectiondetecting process” after Step S42 in FIG. 17 (after the topologydetecting process). FIG. 22 is a flowchart showing an example of theconnection detecting process. At Step S53, the control section 38confirms whether or not there is any destination unconfirmed port (“**”)in the network structure data. In the case where there are destinationunconfirmed ports (“YES” at Step S26), the control section 38 selectsone of the destination unconfirmed ports as a check target port YSP ofthe connection detecting process (Step S54). In this regard, adestination unconfirmed port of the plurality of S ports in each of thesatellite nodes and a destination unconfirmed port of the plurality ofports in the main node are included in the “destination unconfirmedport(s)”.

At Step S55, the control section 38 transmits a connection confirmingcommand for confirming connection to the selected check target port YSPto the satellite node having the YSP, and confirms whether or not thereis a connection confirming response from the other satellite nodes(destination of the YSP) against the connection confirming command.Namely, the main node 60 generates a connection confirming commandincluding a port number indicating the YSP, adds the ID of the satellitenode having the YSP to the connection confirming command to transmit itwith the main packet, and receives a response to the connectionconfirming command. In this regard, in the case where the selected portYSP is a port of the main node 60, at Step S55, in place of transmissionof the connection confirming command addressed to the satellite node, asearch signal the same as a search signal (will be described later) isgenerated to be set to the instruction register 35, the M packetgenerating and transmitting section 34 is caused to generate a satellitepacket including the search signal, and it is transmitted from the YSPimmediately after a satellite packet period.

FIG. 23 is a flowchart for explaining procedures of a process that thecontrol section 17 of the satellite node carries out in connection withthe “connection detecting process”. This process is carried out when theconnection confirming command from the main node 60, which is extractedfrom the main packet, is written into the instruction register 15 andthe control section 17 receives the connection confirming command. AtStep S59, the control section 17 compares the ID added to the connectionconfirming command with its own ID to check whether or not the commandis addressed to the satellite node itself. In the case where theconnection confirming command is addressed to the satellite node itself(“YES” at Step S59), a port number included in the connection confirmingcommand is set to a port number variable PN as a search target (StepS60), and a search signal for searching whether there is connection ofthe node or not is generated (Step S61). The control section 17 thensets the generated search signal to the response register 19, and thecontrol data register 18 and the response register 19 are set up so asto transmit the satellite packet including the search signal from the Sport PN indicated by the port number variable PN (Step S62). Thus, thereceiving and transferring section 12 carries out the process of FIG.20, and generates the satellite packet including the search signal totransmit it from the S port PN (=YSP) at the timing to transmit thesatellite packet (timing of a clock signal of the lead of the satellitepacket period).

In the case where any S port of any satellite node is connected to theYSP, the satellite packet including the search signal transmitted fromthe YSP is received at the S port of the satellite node for thedestination. In the case where the search signal is included in thesatellite packet, the receiving and transferring section 12 of thesatellite node in which the satellite packet is received carries out aprocess of FIG. 24, and writes information indicating that the searchsignal is received and a port number of the received S port into theinstruction register 15 (Step S63). In this regard, in the case wherethe satellite node receives the satellite packet including the “searchsignal”, the transferring process of FIG. 13 is not carried out for thesatellite packet including the “search signal”.

Then, when information indicating that the search signal is receivedfrom the instruction register 15 and the port number are received, thecontrol section 17 of the satellite node carries out a process shown ina flowchart of FIG. 25. Namely, the process of FIG. 25 is a processcarried out by the control section 17 of the satellite node thatreceives the search signal. The control section 17 sets the receivedport number (indicating the port receiving the search signal) to a portnumber variable PN (Step S64), and generates a connection confirmingresponse including the ID of the satellite node and the port numbervariable PN (Step S65). The control section 17 then generates asatellite packet including the connection confirming response, and setsthe response register 19 so as to transmit the satellite packet from theM port (Step S66). Thus, the receiving and transferring section 12carries out the process of FIG. 20, and generates a satellite packetincluding the connection confirming response and transmits it from the Mport at the timing to transmit the satellite packet. Thus, theconnection confirming response is sent back to the main node 60. Here,it should be noted that the response (connection confirming response) tothe connection confirming command is not returned by the satellite nodehaving the YSP, but by the node for destination of the YSP.

Returning to FIG. 22, when the control section 38 of the main node 60receives the satellite packet including the connection confirmingresponse (“YES” at Step S56), information on the satellite node thatsends the connection confirming response back (an ID of the node and aport number variable PN) is recorded in the network structure data as adestination of the check target port YSP (Step S57). Further, in thecase where there is no connection confirming response withinpredetermined time (“NO” at Step S56), it is determined that no node isconnected to the check target port YSP, and “no connect (=Null)” for thecheck target port YSP is recorded in the network structure data (StepS58).

The connection detecting process is repeatedly carried out so long asthere is any connection unconfirmed port, and is terminated when thereis no connection unconfirmed port (“NO” at Step S53). In this regard,although the flowchart of FIG. 22 is drawn so that the connectiondetecting process is continuously repeated so long as there is anyconnection unconfirmed port, the connection detecting process may beinterrupted in the middle thereof and other process may be cutthereinto.

A state where spare wire is detected in the audio network system shownin FIG. 7 by the “connection detecting process” described above will bedescribed. Since there is no connection confirming response to theconnection confirming command for the destination unconfirmed port P1 ofthe main node 60 and the destination unconfirmed S port P3 of thesatellite node 61, “no connection (=Null)” is recorded in the networkstructure data (a state of FIG. 16G).

The destination unconfirmed ports of the satellite node 62 (S node 1)are a S port P2 and a S port P3. In the case where the S port P2 isselected as a check target port YSP, the main node 60 transmits theconnection confirming command for confirming connection of the port P2to the satellite node 62 (with the main packet). In FIG. 7C, abroken-line arrow extending from the S port P2 of the satellite node 62(S node 1) indicates a flow of this “search signal”. The satellite node63 (S node 2) that receives the search signal sends a connectionconfirming response including its own ID (=D) and the port number (Sport P0), from which the search signal is received, back to the mainnode 60 (with the satellite packet). In FIG. 7C, solid-line arrows (anarrow entering the S port P2 of the “S node 0” from the M port P1 of the“S node 2” and an arrow entering the port P0 of the “M node” from the Mport P0 of the “S node 0”) indicate a flow of the connection confirmingresponse. The main node 60 detects that the YSP is a destination of theS port P2 of the S node 1 by means of the connection confirmingresponse. In the network structure data, the “destination ID=D” and the“port number=P0” are recorded for the S port P2 of the S node 1, and the“destination ID=C” and the “port number=P2” are recorded for the S portP0 of the S node 2 (ID=D).

FIG. 7D shows a state where connecting wire (spare wire) between the Sport P2 of the satellite node 62 (S node 1) and the S port P0 of thesatellite node 63 (S node 2) is detected, wherein the detected sparewire is indicated by solid lines (the “route” is indicated by a solidline thinner than the heavy line). At this state, a destinationunconfirmed port of the satellite node 62 (S node 1) is only the S portP3. When the main node 60 transmits a connection confirming command forconfirming connection of the port P3 to the satellite node 62, thesatellite node 62 transmits a search signal (satellite packet) accordingto the connection confirming command from the S port P3 (in FIG. 7D, aflow of a broken-line arrow extending from the P3 of the “S node 1”).The satellite node 63 (S node 2) that receives the search signal repliesa connection confirming response including its own ID (=D) and the portnumber (S port P2), from which the search signal is received, to themain node 60 (in FIG. 7D, a flow of a solid-line arrow entering the Sport P2 of the “S node 0” from the M port P1 of the “S node 2” and asolid-line arrow entering the port P0 of the “M node” from the M port P0of the “S node 0”). The main node 60 detects a destination of the S portP3 of the S node 1 as the YSP by means of this connection confirmingresponse. In the network structure data, the “destination ID=D” and the“port number=P2” are recorded for the S port P3 of the S node 1, and the“destination ID=C” and the “port number=P3” are recorded for the S portP2 of the S node 2 (ID=D).

Hereinafter, all of destination unconfirmed ports are checked in thesimilar manner. When the connection detecting process for all ports ofall nodes in the audio network system is terminated, as shown in FIG.16H, information on the destinations for all ports of all nodes isrecorded in the network structure data. Thus, the main node 60 candetect a whole configuration of the audio network system including notonly topology but also spare wire (redundant section).

According to the connection (spare wire) detecting process describedabove, the main node 60 can detect spare wire of each of the satellitenodes 61 to 64 by a simple communication protocol (“connectionconfirming command” from the main node, “search signal” from thesatellite node and “connection confirming response”). Each of thesatellite nodes 61 to 64 may merely carry out simple processes(transmission of the “search signal” in accordance with the “connectionconfirming command” and transmission of the “connection confirmingresponse” in accordance with the “search signal”), and complex processessuch as a process to detect neighboring nodes that has been carried outwhen to generate a conventional routing table are not required.

By carrying out the connection detecting process for all ports, thecontrol section 38 of the main node 60 can display the spare wiredetected by the connection detecting process on the display section 44so as to add the spare wire to display content of the topology (networkstructure) according to the detection result of the topology detectingprocess described above. Thus, the user can confirm the whole audionetwork system including the spare wire on the display screen of thedisplay section 44. In this regard, the whole display form of the audionetwork system displayed on the display screen may be a form tographically display the audio network system by means of “block images”schematically indicating the nodes and “lines” indicating the cables asdescribed above, or the audio network system may be presented by meansof character information.

In this regard, the control section 38 does not need to wait for updateof display of the display section 44 until the connection detectingprocess for all ports is terminated, and may update display of thedisplay section 44 whenever connection of the destination unconfirmedport is detected, whereby the detection result may be reflected to thedisplay content of the display section 44.

<Operation and the Like by User>

On the display section 44, not only the screen to display aconfiguration of the audio network system, but also a screen to displayother information such as values of various kinds of parameters for eachsatellite node and the like are displayed, for example. The useroperates an operator for screen selection included in the operator 43,whereby switching of screens to be displayed on the display section 44is instructed, for example. When the operator for screen selection isoperated, the control section 38 of the main node 60 carries out controlto change the screen displayed on the display section 44 into a newscreen selected by the operation of the operator (Step S67 in FIG. 26).Thus, the user can switch a screen displayed on the display section 44to a desired screen. In this case, parameters displayed on the screenare respectively assigned to operators for changing values included inthe operator 43. In this regard, by providing one operator for changingvalues and displaying a cursor on a displayed parameter, a parameter ata position at which the cursor is placed may be assigned to an operatorfor changing the value.

By operating one of the operators for changing values to adjust a valueof the parameter assigned to the operator, the user can control anoperation of the main node 60 (in the case where the parameter is aparameter for the main node), or remotely control an operation of anysatellite node (in the case where the parameter is a parameter for thesatellite node). For that reason, the main node 60 stores data onparameters for the main node 60 itself (a kind of parameter, a variablerange of the value of the parameter and the like) and data obtained bycopying data on parameters for the satellite nodes (data on a parameterfor remote control). In a current memory for storing current values ofvarious kinds of parameters, a region for storing the values of theparameters for the main node 60 itself and a region for storing thevalues of the parameters for remote control are provided. The region forremote control is not fixed, and is changed depending on the satellitenodes that exist in the audio network system. Namely, in detection ofthe topology, when existence of a new satellite node is confirmed, aregion for storing parameters for the satellite node is added. Further,when the satellite node that has existed until that time becomes absent,a region for storing parameters for the satellite node is deleted. Onthe other hand, the satellite node subjected to remote control storesonly data on parameters for itself, in the current memory for storingcurrent values of various kinds of parameters, only a region for storingthe values of the parameters for itself is provided.

Further, the parameters of each node are parameters for controlling eachblock of the node (see FIG. 5), and particularly, the parameters of thesignal processing sections 21, 32 include a parameter of the filter forcontrolling frequency characteristics of the audio signal, a parameterof the compressor for controlling compression or expansion of change ina level of the audio signal, a parameter of the delay for controllingdelay of the audio signal, and a parameter of the damper for controllinga level of the audio signal.

Further, in the parameters for the satellite node, a parameter of a“reception channel number” indicating that a signal of any channel ofthe audio signals of the eight channels in the main packet is receivedin the satellite node is included.

FIG. 27 is a flowchart showing a process carried out by the controlsection 38 when an operator for changing a value is operated in the mainnode 60. At Step S68, the control section 38 changes a value of aparameter assigned to the operator in accordance with an operationamount of the operator. In the case where the parameter assigned to theoperator is a parameter for the main node 60 (“YES” at Step S69), thecontrol section 38 controls the operation of the main node 60 on thebasis of a new value of the parameter (Step S70).

Further, in the case where the parameter assigned to the operator is aparameter for the satellite node (“NO” at Step S69), the control section38 generates a value changing command for instructing the satellite notto change the value of this parameter, adds an ID of the satellite nodecorresponding to this parameter to the value changing command, transmitsit with the main packet, and confirms a response corresponding to thecommand (Step S71). Namely, the control section 38 of the main node 60transmits a command for changing a value of the parameter to thesatellite node corresponding to the parameter, and remotely controls theoperation of the satellite node.

At Step S71 as described above, the main packet including the valuechanging command transmitted from the main node 60 arrives at therespective satellite nodes in turn, and in each of the satellite nodesthe value changing command is extracted to be set to the instructionregister 15. FIG. 28 is a flowchart showing a process carried out by thecontrol section 17 of each of the satellite nodes when the controlsection 17 of each satellite node receives the value changing commandfrom the instruction register 15. At Step S72, the control section 17compares the ID added to the value changing command with its own ID tocheck whether or not the command is addressed to the satellite nodeitself. In the case where the command is a value changing commandaddressed to the satellite node itself (“YES” at Step S72), the controlsection 17 changes the value of the parameter instructed to change thevalue into the instructed value (Step S73), and controls an operation ofthe satellite node on the basis of a new value of the parameter (StepS74). The control section 17 then generates a change response includinga result of the change of the value and the ID of the satellite node(Step S75), and the satellite packet including the generated changeresponse is generated to be set to the response register 19 so as to betransmitted from the M port (Step S76). Thus, the receiving andtransferring section 12 carries out the process of FIG. 20, generates asatellite packet including the change response and transmits it from theM port at the timing to transmit the satellite packet. The main node 60receives the satellite packet including the transmitted change response,and confirms the response to the value changing command.

Thus, by operating the operator 43 of the main node 60 and changing avalue of the parameter of the main node 60, the user can carry outcontrol of sound characteristics of the audio signals of the eightchannels to be transmitted from the main node 60 and the like. Further,by remotely changing a parameter of each of the satellite nodes, theuser can select the audio signals that the satellite node receives andoutputs, and control sound characteristics of the audio signals to beoutputted.

As explained above, according to this embodiment, by simple control(FIG. 11) to select one from a plurality of ports in turn and confirmwhether or not the main packet arrives at the selected port everypredetermined period, each satellite node can automatically find anotherport at which the main packet arrives every predetermined period at thepresent stage. Therefore, even in the case where a failure occurs inconnection between nodes in the audio network system, a beneficialeffect is achieved that it is possible to continue reception of a mainpacket and an output of an audio signal without using a routing table.

Further, in the audio network system having a plurality of main nodes,one of the plurality of main nodes carries out a main operation, and theother main nodes carry out a satellite operation. Then, when transfer ofthe main packet is lost on the audio network system, one of the mainnodes that carry out the satellite operation is automatically promotedto a main node, and carries out transmission of a main packet (FIG. 12).Therefore, the present invention achieves a beneficial effect that it ispossible to continue the operation of the audio network system.

Therefore, according to the present invention, a beneficial effect isachieved that, even in the case where a failure occurs on the audionetwork system, it is possible to avoid the failure with relativelysimple control by automatically changing routes (dynamic routing).

Further, according to the embodiment described above, the main node 1generates and transmits the packet including a plurality of clocksignals (in the embodiment described above, 12 clock signals) embeddedat constant intervals (in the embodiment described above, 83.3 μs),which corresponds to the divisor of the packet transmitting cycle (firstperiod (in the embodiment described above, one msec.)) and audio signalsof a plurality of channels. Thus, each of the satellite nodes 2 a to 2 hcan generate the sampling clock (96 kHz) in synchronization withreception timing of each clock signal received every constant interval.In this way, each of the satellite nodes 2 a to 2 h can generate thesampling clock (second clock) on the basis of the reception timing ofthe clock signal at every period (at every constant time interval)shorter than the packet transmitting cycle. Therefore, a beneficialeffect that even in the case where a size of a packet for transmittingan audio signal becomes larger, the sampling clock (second clock) havingsmall lag time with the sampling clock (first clock) of the main node 1can be generated with high stability compared with a conventionaltechnique in which a word clock in synchronization with timing when thepacket reaches the receiving device is generated, is achieved.

Further, according to the embodiment described above, each of thesatellite nodes can automatically find another port that the main packetreaches every predetermined period at present time by simple control toselect one of the plurality of ports in turn, and to confirm whether themain packet reaches the selected port every predetermined period or not(FIG. 11). Therefore, a beneficial effect that even though a failureoccurs in connection between the nodes in the audio network system,reception of the main packet and output of the audio signals can becontinued without using a routing table is achieved.

Further, in the audio network system having a plurality of main nodes,one of the plurality of main nodes carries out a main operation, whileother main nodes carry out a satellite operation. Then, whentransmission of the main packet is lost on the audio network system, oneof the main nodes that carry out the satellite operation isautomatically promoted to the main node that is to carry out the mainoperation and transmits the main packet (FIG. 12). Therefore, abeneficial effect that the operation of the audio network system can becontinued is achieved.

Therefore, according to the present invention, a beneficial effect thateven though a failure occurs in the audio network system, avoiding thefailure (dynamic routing) can be carried out with relatively simplecontrol by automatically changing routes is achieved.

Further, according to the embodiment described above, by detectingtopology (network structure) of the audio network system using thetopology detecting process of FIG. 17, using simple communicationprotocols, such as transmission of the “existence confirming command” bythe main node 1, return of the “existence confirming response” by eachof the satellite nodes 2 a to 2 h that received the “existenceconfirming command” and remote control to “prohibit transfer” for S portof each of the satellite nodes 2 a to 2 h, and transmission of the“existence confirming command” by the main node, return of the“existence confirming response” by the satellite node that received the“existence confirming command”, remote control to “prohibit transfer”for S ports of satellite nodes, and remote control to “prohibitresponse” for each of the satellite nodes, the main node can detectconnection (topology) of all of the satellite nodes on the network. Inthis case, each of the satellite nodes is merely required to carry outsimple processes such as a response to the “existence confirmingcommand” (existence confirming response) and reception of remote controlto prohibit transfer for each of the S ports. Thus, it is no need forthe satellite node to carry out complicated processes such as a processto detect a neighboring node by oneself. Therefore, a beneficial effectthat topology (network structure) of the network system can be detectedwith a simple technique without need to carry out a complicated processat each node is achieved. The method of detecting topology whoseprocedures are shown in FIG. 17 is not suitable for detection oftopology that the system uses to control the nodes, but for detection oftopology that the system presents its users (for example, topologypresented by display on a screen or the like).

Further, according to the present embodiment, by simple communicationprotocols including transmission of the “connection confirming command”by the main node 1, transmission of the “search signal” by each of thesatellite nodes 2 a to 2 h that received the “connection confirmingcommand”, and return of the “connection confirming response” by each ofthe satellite nodes 2 a to 2 h that received the search signal, the mainnode 1 can detect spare wire of each of the satellite nodes 2 a to 2 hby the connection confirming process of FIG. 22. In this case, each ofthe satellite nodes 2 a to 2 h is merely required to carry out simpleprocesses (transmission of the “search signal” according to the“connection confirming command”, and transmission of the “connectionconfirming response” according to the “search signal”), and is notrequired to carry out complicated processes such as detection of theneighboring nodes. Therefore, a beneficial effect that spare wire of thenetwork system can be detected with a simple technique without need tocarry out a complicated process at each node is achieved.

In this regard, although the number of ports of each of the satellitenodes and the number of ports of the main node have respectively beenset to four and two in the embodiment described above, the number ofports of each node may be set to an arbitrary number. For example, thenumber of ports in each of the satellite nodes may be set to ten, andthe number of ports in each of the main nodes may be set to four.

Further, although the number of clock signals embedded in the mainpacket has been set to twelve in the embodiment described above, it isnot limited to this. By setting the number of network clocks of thepacket transmitting cycle (=transferred bit number) to n, it may be asuitable plurality of clock signals embedded at even intervals eachcorresponding to a n/m clock (n, m is an integer). Namely, the pluralityof clock signals embedded in one main packet may be a plurality of clocksignals embedded at constant intervals each corresponding to a divisorof the packet transmitting cycle (first period). In short, the number ofclock signals and a length of the embedded interval are not limited tothose in the embodiment described above. A plurality of clock signalsmay merely be embedded in one cycle of the packet transmitting cycle(first period) at even intervals. Further, the sampling clock and thebit width of the audio signal are not limited to 96 kHz and 24 bits,respectively.

Further, although the packet configuration example in which the data ofthe main packet are divided into the two groups of the even sample groupand the odd sample group has been described in the embodiment describedabove, the data of the main packet may be a packet structure in whichthe data are divided into a plurality (two or more) of groups.

Further, in the embodiment described above, in the topology detectingprocess that has been explained with reference to FIGS. 17 to 21, each Sport of each satellite node has been set to transferable or nottransferable regardless of the kind of received satellite packet.However, the process may be constructed so that only the satellitepacket in which the existence confirming response is included is set totransferable or not transferable. Further, in the connection (sparewire) detecting process that has been explained with reference to FIGS.22 to 25, the case where the satellite node does not transfer thesatellite packet when the satellite packet including the “search signal”is received (the transferring process of FIG. 13 is not carried out) hasbeen explained. However, the satellite packet including the “searchsignal” may also be constructed so as to be transferred from the M portin the transferring process of FIG. 13.

In this regard, so long as the audio network system is constructed byconnecting between one port of an arbitrary node and one port of anotherarbitrary node using the cable, the present invention can be applied toan audio network system having any connection form.

Further, the waiting time at each of Steps S11 and S102 described aboveis merely an example, and is longer or shorter than the exemplified timelength. Alternatively, it may be changed in accordance with setting ofthe user or the circumstances of the time.

Further, with respect to the predetermined value k at Step S107 in FIG.12, the predetermined value k of each main node is set to the same valueinstead of differentiating a predetermined value k set to each mainnode. When the audio network system is turned on or when the network isreset, timing to start the M port number setting task (FIG. 12) may bedifferentiated for each main node.

Further, transfer of all of the satellite packets received at the S portspecified by the command is prohibited on the basis of the prohibitedport data set by the transfer prohibiting command. Since the prohibitionof transfer is originally carried out for topology detection, theprohibited port data need only to work on a satellite packet includingan existence confirming response, which is utilized for the topologydetection. Namely, in the case where a satellite packet including anexistence confirming response is received at an S port, transfer iscarried out only when the S port is not prohibited from transferring bythe prohibited port data. On the other hand, in the case where thesatellite packet including other response data is received at the Sport, transfer may be carried out in spite of whether the S port isprohibited from transferring the prohibited port data or not. In thecase where remote control for the satellite node is carried out whiletopology detection is carried out in the background, such a mannerallows commands from the main node to the satellite nodes to be reduced,and therefore it is far effective.

What is claimed is:
 1. An audio network system comprising: a main nodehaving at least one port; a plurality of satellite nodes each having aplurality of ports; and a plurality of connections each connecting oneport of one node of the main node and the plurality of satellite nodesto one port of another node of the main node and the plurality ofsatellite nodes, wherein the main node comprises: a transmitting sectionconfigured to generate a main packet comprising audio signals, andconfigured to transmit the main packet via the port of the main node,and wherein at least one of the plurality of satellite nodes comprises:a receiving section configured to select one of the plurality of portsof the satellite node, each port capable of both transmitting andreceiving, configured to confirm whether the main packet arrives at theselected port, and configured to, when the main packet arrives at theselected port, receive the main packet via the port by continuing theselection of the port; a transmitting section configured to transfer themain packet received by the receiving section via at least two portsother than the selected port of the satellite node; and an outputsection configured to extract an audio signal from the main packetreceived by the receiving section to output the extracted audio signal.2. The audio network system as claimed in claim 1, further comprising:another main node having one port connected to one port of one node ofthe plurality of satellite nodes by means of a connection, wherein theanother main node comprises: a receiving section configured to confirmwhether or not the main packet arrives at the port of the another mainnode, and configured to, when the main packet arrives at the port,receive the main packet via the port; and a transmitting sectionconfigured to, when the main packet does not arrive, generate anadditional main packet including audio signals in place of the mainnode, and configured to transmit the additional main packet via the portof the another main node.
 3. The audio network system as claimed inclaim 1, further comprising: another main node having a plurality ofports, each of the plurality of ports being connected to one port of onenode of the plurality of satellite nodes by means of a connection,wherein the another main node comprises: a receiving section configuredto confirm throughout the plurality of ports of the another main nodewhether or not the main packet arrives at any one port of the pluralityof ports of the another main node, and configured to, when the mainpacket arrives at any one port, receive the main packet via thecorresponding one port; a first transmitting section configured to, whenthe main packet arrives at the corresponding one port, transfer the mainpacket received by the receiving section via a port other than thecorresponding one port of the another main node; and a secondtransmitting section configured to, when the main packet does not arriveat the corresponding one port, generate an additional main packetincluding audio signals in place of the main node, and configured totransmit the additional main packet via the plurality of ports of theanother main node.
 4. The audio network system of claim 1, wherein themain node further comprises an input section that inputs the audiosignals to the main node.
 5. The audio network system of claim 1,wherein the output section is further configured to extract the audiosignal of a desired channel from the main packet.
 6. A method of asatellite node, the method comprising: selecting one of a plurality ofports of the satellite node, each port capable of both transmitting andreceiving, to receive a main packet from a main node; confirming thatthe main packet arrives at the selected port; receiving the main packetvia the port by continuing the selection of the port; transferring themain packet via at least two ports other than the selected port of thesatellite node; and extracting an audio signal from the main packet tooutput the extracted audio signal.
 7. A satellite node comprising: areceiving section configured to select one of the plurality of ports ofthe satellite node, each port capable of both transmitting andreceiving, configured to confirm whether the main packet arrives at theselected port, and configured to, when the main packet arrives at theselected port, receive the main packet via the port by continuing theselection of the port; a transmitting section configured to transfer themain packet received by the receiving section via at least two portsother than the selected port of the satellite node; and an outputsection configured to extract an audio signal from the main packetreceived by the receiving section to output the extracted audio signal.